Lightning Safety of Animals

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International Journal ofBiometeorology ISSN 0020-7128Volume 56Number 6 Int J Biometeorol (2012) 56:1011-1023DOI 10.1007/s00484-011-0515-5

Lightning safety of animals

Chandima Gomes

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ORIGINAL PAPER

Lightning safety of animals

Chandima Gomes

Received: 17 September 2011 /Revised: 3 December 2011 /Accepted: 5 December 2011 /Published online: 5 January 2012# ISB 2012

Abstract This paper addresses a concurrent multidisciplin-ary problem: animal safety against lightning hazards. Inregions where lightning is prevalent, either seasonally orthroughout the year, a considerable number of wild, captiveand tame animals are injured due to lightning generatedeffects. The paper discusses all possible injury mechanisms,focusing mainly on animals with commercial value. A largenumber of cases from several countries have been analyzed.Economically and practically viable engineering solutionsare proposed to address the issues related to the lightningthreats discussed.

Keywords Lightning injury . Animal safety . Step potential .

Side flashes . Direct strikes . Preventive measures

Introduction

Lightning is a phenomenon based on atmospheric elec-tricity that brings extremely large impulsive currents toearth. A living being can be affected by lightning inseveral ways. There are numerous papers published onthe mechanisms of lightning injuries to human beings(Gomes and Kadir 2011; Cooray et al. 2007; Zimmermannet al. 2002; Norman et al. 2001; Carte et al. 2002;Muehlberger and Vogt, 2001; Elsom 2000; Fahmy etal. 1999; Webb et al 1996; Andrews 1992; Mackerras1992; Duclos and Sanderson 1990; Andrews and Darvaniza

1989; Epperly and Stewart 1989; Coorper et al. 1989;Eriksson and Smith 1986; Cooper 1980) which are grosslyapplicable to animals as well. However there are some specificinjury probabilities that should be consideredwhen it comes tolightning safety of animals.

Every year thousands of cattle, buffalos, sheep, goats,etc. succumb to lightning injuries all over the world.Animals are much vulnerable to be affected by lightningas they are usually placed outdoor even under thunder-storm conditions. Occasionally, precious animals such aselephants, horses, etc. are also subjected to lightningrelated injuries. Especially, animals having a large sepa-ration between their front and back feet such as ele-phants, cattle, horses, donkeys, etc. are vulnerable toreceive lightning injuries due to the dangerous potentialdifferences that may built up between these feet, in theevent of nearby lightning.

There are several case studies done on the lightningeffects on four legged animals which have been publishedas research papers (Žele et al. 2006; Boeve et al. 2004; VanAlstine and Widmer 2003; Bedenice et al. 2001; Williams2000; Appel 1991; Ishikawa et al. 1985; Karobath et al.1977; Brightwell 1968; Best 1967). All the above papersdiscuss medical aspects of lightning injuries or injury mech-anisms and hardly made attempts to provide technicallyviable solutions to minimize the lightning hazards. In fewpapers some precautionary measures are briefly explained.In this paper we provide a comprehensive account on thelightning injury mechanisms with an engineering perspec-tive and describe practical solutions to minimize lightninginjuries on captive and movement-controllable animals.Contents of the paper will have valuable applications inlivestock industry, game parks, zoological gardens and allactivities where animals are involved.

C. Gomes (*)Department of Electrical and Electronics Engineering,Centre of Excellence on Lightning Protection (CELP),Universiti Putra Malaysia,43400, Serdang, Selangor, Malaysiae-mail: [email protected]

Int J Biometeorol (2012) 56:1011–1023DOI 10.1007/s00484-011-0515-5

Author's personal copy

Information analysis

Lightning threat

Lightning is a short duration (40–70 μs) transient currentwhich may flow to ground several times during a singleflash. It is a double exponential waveform, sometimesfollowed by slow varying downward ramp (known ascontinuing current) that has much smaller magnitudethan the peak of the initial impulse. The initial impulseshave about 30 kA peak value on average whereas ex-treme values, which are in the order of many 100s ofkilo-amperes, have also been detected. The continuingcurrent may last from a few milliseconds to 100s ofmilliseconds and have magnitudes in the order of a fewto several hundred Amperes. The impulse-continuingcurrent combination is called a stroke. In a single flashmany such strokes can reach ground with temporal sep-aration of a few to few hundred milliseconds. On aver-age, a negative lightning has 3–4 strokes. Positivelightning, which brings impulse currents of much largeramplitudes and continuing currents of longer durationsand higher magnitudes, usually has one stroke per flash(Cooray 2003). Positive lightning contributes to less than5% of the ground flashes in the tropics, whereas they canbe as high as 40% in temperate regions and in winterstorms in Japan and Korea (Cooray 2003).

Lightning current maintains a constant value as itflows through an object at ground level (such source istermed a current generator). Hence, the lightning struck

object develops a short-term potential difference betweentwo parts of it along the path of the current. The top ofthe tree shown in Fig. 1 develops a very high potentialwith respect to a distant point at ground, when it isstruck by lightning. The magnitude of this potentialdifference depends on the impedance (basically due toseries resistance and inductance) between the two pointsof the object and the magnitude and time derivative ofthe current. For example, when lightning current flowsalong highly resistive (let’s ignore the inductance forconvenience) material such as the wood of a tree, thepotential difference generated will be very high. Forlightning with large currents this potential differencemay reach values exceeding megavolts if the two pointsof concern are far apart. In such cases not only thepotential difference but also the heat generated will bemassive. On the other hand when the lightning currentflows along a good conductor, such as a copper rod thepotential difference between two points separated by asimilar distance, as in the previous case, will be muchless, thus the heat dissipation will also be very small.This observation is the basic concept of lightning pro-tection systems which will not be covered in this paper.

The potential at the point where the lightning currententers ground is usually at a large value, typically in theorder of several tens of kilovolts. This potential rapidlydecreases as one moves radially away from the point ofinjection of current to ground, giving rise to a so-called“ground potential gradient” as shown in Fig. 1a. This po-tential gradient becomes significantly large if the earth re-

Fig. 1 a The distribution ofpotential when a tree is struckby lightning. b An animal in thedirection of potential gradient issubjected to step potentialhazard

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sistance of soil is high. A potential gradient causes surfacecurrents to flow in many directions from the point of strike.In some experiments done on artificial lightning (triggeredlightning), it has been observed that lightning may generatesurface flashover (current that flows on ground surface inthe form of sparks) that extends to more than 20 m. Therefore,in the subject of lightning safety this potential gradient plays asignificant role.

Injury mechanisms

To be injured or temporarily disabled, an animal may notessentially be struck by lightning. Even if it is close to thepoint of strike it may receive lethal injuries to which thevictim may succumb.

Lightning may injure or kill animals, basically in severalprimary ways:

Direct strikes An animal in the open field who keeps itselfas a high protrusion in the vicinity may be the subject of adirect lightning strike if the answering leader from theanimal meets lightning stepped leader. In such an event,the entire lightning current may pass through or overthe body of the victim. The greater the height of theobject above others in the vicinity, the higher the chan-ces that it receives a lightning strike, although severalother parameters also contribute to the selection of theobject being struck.

Side flashes Animals underneath a large tree, large poleor inside a tent on wooden poles may receive a side flashif the tree or the tent is hit by lightning. In such casesthe entire lightning current or a part of it may passthrough the victim’s body. Figure 2 shows such a possibility.

The closer the animal is to the parts of the originallylightning struck object, the greater the chances of it getting aside flash.

Step potential This is the most common lightning hazardamong four-legged animals. When the feet of an animalare separated in the direction of increasing potential, apartial current may pass through the body if the twoparts of the body in contact with the ground align inthe direction of potential gradient developed due to theinjection of current into the earth from a nearby lightningstrike. Figure 1a depicts how the potential distributesduring the passage of lightning current, and Fig. 1bshows how an animal in the direction of the potentialgradient is subjected to partial currents. In contrast to thecase of human beings, lightning current entering fromone set of feet of animals may cross over heart, liver, etc.as the path of current will be through these organs.Note that even when the animal is in 90° to the givenposition it will be subjected to the step potential thatdevelops between its left feet and right feet that maysend lethal current through the same organs mentionedbefore.

Touch potential A partial current may pass through the bodyof an animal, if a part of the body comes in contact withhigher elevation of the lightning struck object while theother part remains in contact with ground (refer Fig. 1a).Most often animals with high vertical stretch (giraffes andelephants) are subjected to serious touch potential hazards.Figure 3 depicts how an elephant reaching high branches ofa tree while its feet are at ground level may get part of thelightning current due to touch potential. As the lightning

Fig. 2 The possibility of an animal getting a side flashFig. 3 The possibility of an animal getting a partial lightning currentdue to touch potential

Int J Biometeorol (2012) 56:1011–1023 1013


current flows through the tree a large voltage develops alongthe trunk of it. As a part of the elephant is in contact with theupper parts of the tree it will be exposed to touch potentialwhich may be fatal.

Upward streamers As the lightning stepped leader rea-ches ground from cloud, usually carrying negativecharge, it creates an intensive electric field in the vicin-ity. Hence, many objects in the surrounding starts send-ing oppositely charged streamers towards the steppedleader. Once one of those answering leaders is success-ful in meeting the stepped leader the others vanish.These answering leaders give rise to a small currentthrough the body of objects that send them. Such cur-rent may most often paralyze the animal; however,depending on the heart cycle that it passes through,even serious injuries or cardiac failure may result. Chan-ces of upward streamer related hazards are rare compared toother mechanisms.

Proximity to the strike The shock wave generated by light-ning channel due to sudden expansion of air may damagethe skin or ear drums when an animal is very close to thepoint of strike. Furthermore, intense light may cause visionimparity of the animals close by.

There are several secondary effects, such as falling fromhigher elevations due to momentary shock, falling of heavymaterials from structures (detached due to lightning strike)on the animal, falling of tree branches and missiling of split-fractions of lightning struck trees, burns and choking hazardsdue to volatile materials in the surrounding catching fire andpsychological trauma, etc.

The passage of current inside the body may lead the animalinto ventricular fibrillation (unsynchronized muscle operationof the heart), respiratory arrest (inability to breath), burning ofvital organs such as brain, liver, kidneys, etc. and internalbleeding due to bursting of blood vessels, mechanical lesionsof internal organs and hemorrhages. The animal may alsosuffer from nervous system damage, broken bones and lossof hearing or eyesight. Lightning injuries can lead to perma-nent disabilities or death. In the case of human beings, onaverage, 20% of strike victims die and 70% of survivors sufferlong-term disabilities (Cooper 1980). The above describedinjuries are primarily neurological, with a wide range ofsymptoms, and are sometimes difficult to cure. Based on theresults of animal experiments, Karobath et al. (1977) state thatsometimes autopsy is incapable of giving recognizablechanges in some of the lightning victims.

Most often lightning accidents are reported in popularmedia rather than in scientific literature. However, thereports sometimes are detailed enough to make conclusionson the injury mechanism. Table 1 depicts some of theseaccidents reported both in published literature and in news

media. In some cases, more than one source have beenreferred for the event analysis; however, only the mainsource was indicated as the source of information.

Analysis of experimental observations

Experiments done in Japan between the 1960s and 1980s byapplying laboratory sparks that simulate lightning to ani-mals have revealed much information on the lethal energy ofimpulse currents in the body (Ishikawa et al. 1985; Nagai etal. 1982; Ohashi et al. 1978, 1981a, b; Kitagawa et al.1972). Studies described in Ishikawa et al. (1985), Nagaiet al. (1982) and Ohashi et al. (1978, 1981a) reveal that thelethal impulse energy depends on the mass of the animalbody. They have shown consistent value around 60 J/kg asthe lethal energy that may kill the animal. The findings ofIshikawa et al. (1985) reveal that when negative repetitiveimpulses (duration 40 μs and rise time 1.5 μs), separated by40 ms, are applied there is no cumulative effect on theanimal. In other words, when impulses below the thresholdamplitude are applied animals have not been affectedlethally. Thus, under natural lightning conditions theeffects of an animal being killed by the lightning cur-rent do not accumulate with increasing number ofstrokes; however, it increases the probability of a strokehaving above threshold energy. It should also be notedthat once the current waveform and its amplitude is fixed, thelethality has another dependent parameter: the current pas-sage. In the above animal experiments, voltage is alwaysapplied between head and a hind legwhich ensured the currentpath to be across the brain and most probably the heart as well.Therefore, in a natural scenario the lethal energy may behigher.

The mean energy per unit resistanceRi2dt

� �of impulse part

of the lightning current is about 50 kJ/Ω for negative lightningand about 600 kJ/Ω for positive lightning (Berger et al. 1975;Anderson and Eriksson 1980). The resistance of a humanbody from head to feet is about 1000 Ω (Berger 2007).Therefore, if the total lightning current flows through thebody, the energy dissipation of a person of mass 50 kg willbe about 1MJ/kg for an average negative first stroke. Evenfor an Asian elephant, of which the body mass isapproximately 5000 kg, the energy dissipation will beabout 1 kJ/kg. As this value is much higher than thelethal energy required to kill the animal, once subjectedto a direct strike it has almost zero chance of survival.However, as we have discussed earlier only about 20%of the direct strike recipients succumb to injuries (Cooper1980). The reason is very obvious as per the discussionbelow.

The answering streamer that emerges from the bodywhich sends an opposite charge towards the steppedleader will contribute to filamentary streamers emanating



from ground and following paths via both internal bodyand external surface. Once the stepped leader is connectedwith the answering leader, the current starts increasing along

both passages. However, due to wetness, salinity, contami-nants, etc. in the external path, a larger part of the current willtake that passage. As the current in these filamentary channels

Table 1 Summary of lightningrelated animal accidents Case

numberIncident Source of information

1 One elephant belonged to a circus died while inopen space

“Death by lightning for giraffes, elephants,sheep and cows”, Tetrapod Zoology, July 15,2009

2 One elephant belong to a circus died while inopen space

“Famed elephant killed by lightning in west”,The News-Sentinel, September 7, 1943

3 One elephant belonged to a Buddhist Templedied while tied to a large tree

Personal observation by the author

4 Five wild elephants died while in an open riverbed

“Elephant grave yard”, Nature Shock inChannel 5, 30th July 2010

5 One tamed giraffe died in an animal park whileit was ambling among trees

“TV giraffe killed by lightning”, TheTelegraph, 09 November, 2010

6 Six sheep in the livestock industry died whileseeking shelter under an isolated tree

“Lightning kills six sheep at Aveley Ranch”,Clearwater Times, August 01, 2011

7 Three pigs in the livestock industry sustainedmultiple fractures of lumbar vertebral bodywhile in an open pen

Van Alstine and Widmer (2003)

8 One pig died and 47 pigs had broken boneswhile in an enclosed barn (in livestockindustry)

Brightwell (1968)

9 Three Holstein-Friesian cattle died and 15 hadvision imparity, diarrhoea, etc. while theywere grazing in pasture (in the livestockindustry)

Boeve et al. (2004)

10 Five pigs were dead and 59 paralysed, while inan enclosed barn (in the livestock industry)

Best (1967)

11 Seven deer belonging to a national park whilein an open field

“Lightning strike kills deer in KenoshaCounty”, Journal Sentinel, March 22, 2011

12 Two wild roe deer died in an open space withlow bushes

Žele et al. (2006)

13 Two domesticated horses had short-term neu-rological impairment while in an open spacenot far from trees

Bedenice et al. (2001)

14 18 cattle in the livestock industry died veryclose to a large isolated tree

“Humphreys farmer says 18 cattle killed bysingle lightning strike”, Humphreys County,TN (WSMV), Aug 13, 2011

15 16 cattle in the livestock industry died veryclose to an isolated tree

“Lightning strike kills bullocks”, BBC News,15 June 2009

16 52 cattle in the livestock industry died while incontact with an ungrounded metal fence in anopen field

“Fifty-two cows are killed after lightning hits awire fence”, the telegraph, 23 October, 2008

17 15 cattle in the livestock industry died in anopen space

“Lightning kills 15 head of cattle in Lithia”,The Tampa Tribune, June 18, 2009

18 Seven cattle in the livestock industry died in anopen space

“Lightning strikes kill child, cattle”, NewVision (Uganda), 30th June, 2011

19 11 sheep in the livestock industry died in anopen space with tall trees not far away

“Lightning kills 11 sheep at East Coventryfarm”, The Mercury, June 29, 2011

20 Eight bighorn sheep in the livestock industrydied in an open space with a tall tree not faraway

“Lightning kills bighorn sheep on WildhorseIsland”, Montana Living, August 10, 2010

21 654 sheep in the livestock industry died on anopen hilly terrain

NOAA, National Weather Service ForecastOffice, Salt Lake City, Utah, USA

22 850 sheep in the livestock industry died on anopen hilly terrain

NOAA, National Weather Service ForecastOffice, Salt lake City, Utah, USA



increases a potential will be built up across the point ofattachment (usually the head or an upper part of an animal)and ground contact point (usually the feet). Once the electricfield due to this potential difference exceeds about 450 kV/m,air on the external body collapses, giving rise to a surface arc.At this instant impulse current through the body of an animal

whose current entrance and leaving points are 2 m apart,reaches about 900 A.

The Toepler’s Law (Toepler 1906) states that theresistance of an electric arc at a given time is inverselyproportional to the charge which has flown through thearc.

i:e: RðtÞ a lRt

0

i ðtÞ dtwhere RðtÞ is the resistance at time t and l is the arc length

Thus, as the current in the arc increases (and the time iselapsed) the resistance of the channel rapidly decreases.Therefore most probably the maximum impulse current thatflows through the internal body will be the 900 A whichexist immediately before the arc is formed. This currentmagnitude is reached within about 0.1 μs. Now, assuminga right angled triangle waveform, where the total energydissipation per unit resistance (ER) can be approximated byER ¼ 1

3 i0 t0 where i0 and t0 are 900 A and 0.1 μs, respec-tively, it is found that the total energy dissipation in the1000 Ω resistance of the body is about 270 J. For an animalof weight 50 kg this is equivalent to energy per unit mass(EM) of about 5.4 J/kg. As the current reaches the maximumvalue, the resistance of the arc channel across the animalbody reduces to about 2 Ω; thus, at peak current of 30 kA,potential difference across the body becomes 60 kV, thatresults in a maximum current of 60 A across the body. Nowagain considering a triangular wave shape of total duration40 μs, we find that there is an energy dissipation of 36 Jinside the body because of the formation of the external arc,which gives rise to a value of EM of 0.72 J/kg. Hence, duringthe total period of the impulse the internal energy dissipationis just above 6 J/kg which is one order less than the lethalenergy per unit mass.

The following points should be noted with regard to theabove calculations:

1. It should be taken into account that the above results areobtained by considering average lightning current am-plitude. There is a small probability of receiving light-ning currents having peaks in the order of severalhundred kilo-amperes. In such cases, the through-bodycurrent during the surface-arc phase may reach valuesseveral times greater than the 60 A value obtained in thecalculations.

2. Continuing current is not taken into account in theanalysis. However, if the surface-arc starts during theimpulse current phase most of the continuing currentwill flow through the arc channel.

3. In the event of a positive lightning, the situation may beworse due to two reasons. Currents of positive lightning

have larger amplitudes and slower current fronts. Thelarger impulse amplitude gives rise to greater through-body currents during the arc phase, whereas slowerfront times allow longer time of flow of pre-arcthrough-body current. Both may adversely affect thechances of survival of the victim.

4. Even smaller currents during a short interval may causecardiac arrest if the flow coincides with critical phasesof the pulmonary cycle. This is one crucial point due towhich the energy per unit mass alone cannot be taken asthe sole pointer of deciding the lethality of lightning.

The above discussion clearly shows that the decisive factorof determining the fate of the lightning victim is the surfacearc formation. A delay of such by few microseconds maycause the current adversely affecting the cardiac cycle or theenergy per unit mass exceeding the lethal threshold. Theexperimental evidence provided in Nagai et al. (1982) alsojustifies that delay in the formation of surface arc causes thedeath of rabbits, especially due to cardiac arrest. In the case ofhuman casualties there are many observations of no signs ofcurrent entrance into the body (personal communications withProf.MaryAnn Cooper, University of Illinois and informationgiven in Gomes et al. 2006). This may most probably be dueto the delayed surface arcing that drives currents sufficient forarresting the heart but insufficient to make burn-through.

The above discussion also explains why the touch poten-tial, step potential and upward streamer related accidents areequally lethal for animals as the direct strikes and sideflashes where the victim is encountered with almost theentire lightning current. In the three former cases thethrough-body current will only be a small fraction of thetotal stroke current; however, due to the very slim possibilityof such currents forming sufficiently high potential differ-ences to generate surface arcing, the current passage willexist for the entire duration. In the case of four-leggedanimals the path of the current will most probably bethrough the heart which creates cardiac arrest. The currentmay also affect spinal code and cervical, thoracic and lum-bar segments causing hind leg paralyses, commonly seenamong animals subjected to step potential.



The current during contact and touch potentials stronglydepends on the contact resistance at current entrance andexit points. The contact resistance may significantly reducewhen the feet are in water or slurry of mud, or a part of thebody is in good contact with a metal component of theobject struck by lightning (e.g. metal pole, fence, etc.).

Analysis of lightning accidents

The information depicted in Table 1 provides technicalinsight to the animal injuries due to lightning. The eventdescribed in case 1 in Table 1 occurred in the Oquawkastown square, in Illinois, USA, in 1972, where the elephanthas been struck by a direct stroke. It was killed on the spot.The case reported in case 2 occurred in Dilion, Montana,USA in 1943. As per the report the victim was struck bylightning and was killed instantly while elephants in thegroup around were paralyzed temporarily. The incident giv-en in case 3 took place in Kandy, Sri Lanka in 2001, inwhich a sacred elephant belonging to the Temple of Toothwas killed by lightning. In this case the scenario of lightningimpact was different to the two cases described above. Theelephant was tied to a tree by a hind leg. There was visualevidence that the tree has been struck by lightning. Therewere no signs of a side flash entering the body, however, aswe have described earlier it is quite possible that lightningcurrent can enter the body by a side flash or direct strikewithout having evidence of entry point. The damage to thechain verifies that current had entered the leg through touchpotential. A possible mechanism for the current transfer isdepicted in Fig. 4. The amplitude of current through thebody depends on various parameters: amplitude of originalcurrent, surface arcing, contact resistances between tree andchain or chain and leg, body resistance and contact resis-tance between feet and ground. Among the four feet, contact

resistance of the hind feet, to which the chain was tied,played a vital role in determining the magnitude of the bodycurrent. Most often elephants are seen either lifting or loose-ly resting the chained foot on ground, most probably due tothe itchy feeling. Furthermore, in the event of a newlystarted rain, the hind legs, which are closer to the tree,may be on relatively dry ground. Due to both of thesereasons, the contact resistance (with ground) of other feet,especially the front feet, may be considerably less than thechained hind foot. Such condition may lead lethal currentsdriven through the elephant’s vital organs.

The death of five wild elephants (case 4) was reported in2007, in the village of Kumargram, West Bengal, India. Theelephants were found dead in the dry bed of Raidak River inthe morning which followed a night of intense thunder-storm. There were speculations of animal poisoning as thecause of death but the necropsy revealed that there were notraces of poisonous substances in the bodies or any otherexternal wounds. Hence, the cause of death had been con-firmed as lightning. Our experience in the soil resistivitymeasurements of dry river beds in Sri Lanka (a countryadjacent to India) shows that in such locations the soilresistivity is very low, in the range of few Ohm meters(unpublished data pertinent to an ongoing project). Theresistance may be even lower in the above case as theincident occurred in heavy stormy conditions with intenserain. Hence, the chances of step potential killing the fiveelephants are remote. This leaves the only possible mecha-nism as direct strike with multiple terminations (fork light-ning) or a direct strike to an elephant followed by severalside flashes (due to their proximity).

The death of a giraffe (case 5) took place in Glen Africreserve in South Africa in 2010. The victim was a popularcharacter in a tele-drama series and was regarded as a veryvaluable asset. The giraffe has been struck by lightningwhile it was ambling through the trees of the nature parkwhile the rest of the TV crew was filming another part of thetelevision show. It was probably subjected to a side flash ofa lightning that struck a tall tree as per the description of theaccident environment.

The event record presented in case 12 (Žele et al. 2006)describes the pathological and histo-pathological examinationof two female roe deer that had been found dead after a severethunderstorm in an open field in Slovenia. The two animalswere found about 1.5 m apart. As per the conclusion of theresearchers, one of the deer was killed by a direct strikewhereas the other was killed by step potential (ground currentas they term). As per their description the trachea and bronchiof both deer contained aspirated light red foam. The proximityof the bodies of the animals and the red foam in the breathingsystem suggest that multiple-termination direct strike or directstrike/multiple side flash combination was more likely theevent rather than a direct strike/step potential combination.

Fig. 4 The possible paths of current due to touch potential as ananimal is tied to a tree by a metal chain



The forensic diagnosis presented in case 8, with regard to48 pigs affected in Ontario, Canada (Brightwell 1968), threepigs affected in Indiana, USA (case 7, Van Alstine andWidmer 2003) and 64 pigs affected in Manitoba, Canada(case 10, Best 1967) shows that the animals have beensubjected to step potential rather than direct strike or sideflash. The hind limb paralysis shown by all surviving vic-tims and evidence of lightning striking nearby objects areevidence of step potential. The animals in each case werefound in a bunch. The small height of swine reduces theprobability of having side flashes. The situation described in29 shows that the lightning had struck the power systemwhich had destroyed a nearby transformer and a part of thecurrent had been transferred to the vicinity of the swine by apower line of which the insulation had been burnt.

The deaths of bighorn sheep reported in Montana, USA(case 20) demonstrate copybook style step potential hazard. Inthis event, there were signs of damage in a large Ponderosapine tree due to lightning and six of the rams were found deadin a circle of about 15 feet (about 5 m) around the tree. Twoother dead bodies were found a few meters away from thecircle. In homogenous ground, the maximum potential gradi-ent can be seen in a direction radially away from the point ofstrike. In this case, unfortunately, the animals happened to bein this ideal direction to receive the maximum surface currentdriven through their bodies. The death of 11 sheep, reported incase 19, is another incident that resembles the above. Theaccident took place in a small wood in East Coventry, USA. Inthis incident too, the sheep were found dead in a circle and atall tree within the circle bore signs of a lightning strike (burnmarks and split branches). The sheep may most probably havebeen killed due to step potential. However, there are chancesof side flashes as well, due to the close proximity of sheep tothe tree in contrast to the previous incidents.

In an incident somewhat similar to the above, in a field inEast Lothian, Florida (case 17), 15 cattle were dead after athunderstorm. The bodies were found almost touching eachother. The animals were in an open field, however a solitarynot-very-tall tree could be observed in the photographsissued, about several tens of meters away from the animals.A lightning expert visited the scene and suggested the causeof death as a direct strike. Although a multiple-terminationdirect strike is not impossible, a direct strike/multiple sideflash is more likely due to the close proximity of the ani-mals. Note that once an answering leader, which will even-tually be successful in meeting the lightning stepped leader,is formed, it is highly unlikely that many such similarsuccessful leaders are formed within a small area. In thecase described in case 17, the step potential hazard due tolightning that struck the nearby tree can also be a possiblecause of deaths. The incidents reported in cases 14, 15 and18, may be either due to side flash or step potential as in allcases the animals were very close to tall trees.

The incident reported in Wisconsin, USA (case 11) is aninteresting event where step potential hazards were evidentas the causes of deaths. In this accident seven deer werefound dead in a large open field. Six of them were huddledin a circle and the seventh was found some distance away.One of the newsfeeds has described that there was a hole ofdepth about 5 inches and diameter of the same size situatedin the middle of the circle; thus, it seems that the incident ismost probably a step potential hazard. The communicationthat we had with two eyewitness of the aftermath (Mr.Randy Lantz and Ms. Jennifer Niemeyer), revealed someaccurate details of the incident which were slightly differentfrom several descriptions in the newsfeeds. The bodies ofsix deer were in a near circle (more of an oval) as shown inFig. 5a. As a witness of the dead animals suggested, light-ning may have struck the deer shown at point Y in Fig. 5aand b. However, as there were no burn marks in the fur (dueto flashover), or any other signs such as red patches, it is notvery convincing to conclude that the deer has been affectedby a direct strike. On the other hand, the disturbance of soilfrom point X to point Y reveals that the lightning may mostprobably have hit the ground at X and a heavy component ofthe surface current has flown in the direction of the deer atY. Thus, the deer had been subjected to a large step potentialdue to which a considerable current had been driven throughits body. The degree of soil disturbance between X and Yhints that if the deer had been struck by the lightning itshould have left at least a few marks on the body of theanimal. It is believed that it was raining by the time of strikeand the deer were wading in standing water of a few centi-meters deep. Figure 5c shows the marks of hooves deeplyembedded in the ground. The seventh victim seems to be inthe same circle by the time it was affected but had managedto walk for about 100 m before it collapsed. This deer wasbleeding from its eyes still on the following day when theincident was brought to the notice of the authorities(Fig. 5d). In general, the description shows that the sevendeer had been subjected to step potential due to the lightningthat struck inside their circle. The firm contact of their feetwith ground had reduced the contact resistance, enhancingthe chances of a large current flowing across their bodies.Unlike in the case of the two-legged animals, the animalswith four legs are subjected to almost the maximum poten-tial gradient across one of many combinations of two legsirrespective of the position of the lightning. Most of thesecurrent paths cross through the vital organs of the bodyreducing the chances of survival of the affected animal. Thisexplains the mass-scale deaths of animals, depicted inTable 1. In a herd of hundreds of animals one cannot expectall the animals in a single direction at the time of strike, stilleach may get enough dose of electricity that exceeds lethalenergy. The deer which was bleeding from the eyes mayhave the current path through or close to the eyes so that



capillaries are crushed due to the impact of heat dissipation(personal communication with Prof. Diana Žele, Universityof Ljubljana). One probable scenario may be the entrance ofcurrent through the legs and leaving through the face as thedeer is keeping its face in contact with or close to ground (e.g. drinking water). There is a possibility that the arcing hadtaken place through its eyes to ground.

Both mass-scale deaths of sheep reported in cases 21 and22 occurred in Utah, USA in the first half of the 19thcentury, in 1918 and 1939. The earlier incident had takenplace at the peak of Mill Canyon, in the American ForkCanyon. The later was reported at the top of Pine Canyon inthe Raft River Mountains. Our experience in many countries(during the inspection visits) reveals that soil resistivity ofmountain pinnacles is much higher than the same at themountain base. This is due to the soil erosion that exposesthe high resistive rocky parts. Hence, the deaths of animalsmay most probably be due to step potential. As it wasdiscussed earlier there is no need for the four-legged animalsto be in one direction to experience high ground potentialgradient. Furthermore, any other lightning injury mecha-nism giving rise to such large number of deaths of animals,spread over a vast land area, is highly impossible.

The hind limb paralysis, visionary imparities and otherneurological deformities detected in the surviving victimsgiven in the diagnosis reports in case 9 on the 18 Holstein-Friesian cattle and in case 13 on the two horses show thatthe majority of animals had been subjected to step potential,effects of intense light and shockwave of lightning thatstruck in the proximity.

The photographs issued by several sources with referenceto the incident described in case 16 show that the 52 cattlewere resting (or in contact with) their faces on the wires of

the metallic fence during the lightning strike. They werefreely gazing in a large landscape on a mountain slopewhich is bound on one side by the fence with metallic wires(on wooden poles). This is an ideal example of death due totouch potential. As there are many parallel paths with rea-sonable conductivity for the lightning current to flow intoground (through the bodies of cattle), surface flashing toground may have not occurred once the lightning currententered the wired fence. It was surprising to observe that theentire herd of cattle (which were free to move away from thefence) was in contact with the wire fence at the time ofstrike. To understand this behavior of the cattle, we com-municated with several dairy farm owners. As per the infor-mation we received, it is a common observation that duringthe thunderstorm periods, the animals either crowd them-selves under large trees (if such trees are at reachable dis-tance) or move towards the peripherals of the landscapeuntil they press themselves into the boundary lines. Thisbehavior seems to be common among horses, sheep andgoats, etc., as well.

Discussion

Accuracy of reporting

The number of peer reviewed research papers available onlightning accidents of animals is somewhat rare. As many ofthe lightning incidents reported in popular media are com-piled by writers of non-scientific background (at least non-lightning experts), sometimes the reports are distorted toenhance the amusement. One such case is the attributionof the cause of death of 84 sheep to ball lightning (information

Fig. 5 The death of deer in theincident in Kenosha County. aThe circle of six deer carcassesafter the incident. b Thedisturbance of soil due to thelightning strike. c The marks ofdeep embedded hooves. d Theseventh deer which had walkedabout 100 m from the circlebefore it collapsed



extracted from “Ball lightning kills 84 sheep in Tuva”, TuvaOnline, 27 July 2011). The incident occurred in Tuva, Russiawhere the animals had been killed while they were seekingshelter under a 15-m tall pine tree. The tree had been split intoparts coinciding with a huge explosion, which the writerdescribes as due to the ball lightning. It is very much evidentthat such incidents are possible only with lightning strikes(Heidler et al. 2004) and the sheep had been killed by steppotential or side flashes. The same article also states that in asimilar incident in 2007, in Dagestan, Russia a herd of 300sheep and the shepherd were killed; most probably anotherincident of step potential hazard similar to the examples givenin Table 1.

Economical impact

It is evident from over 1,000 papers published on lightningprotection of equipment and systems, most often people aremore concerned about the damage (financial losses) tobuildings and equipment. However, our investigations re-veal that sometimes loss of animal may cause much highereconomical impact than property damage. For example, thedeaths of domesticated and trained elephants and the giraffespecified in Table 1 may have caused a loss of about USD20,000–50,000 in each case. Especially, in the case of thedeath of the giraffe (case 5) there were many consequencesthat led to financial losses as the animal was playing a maincharacter in a television series that had been televised duringthe time of tragedy. The death of cattle described in cases14, 15 and 17 cost the respective farmers over USD 20,000or equivalent in each case as per the claims. In another eventthat was not included in Table 1, Sunburnt Land, a racehorse who earned nearly $380,000 in prize money, waskilled by lightning, in Newham, Australia in 2008 incurringheavy losses to the owners (information from “Newhamhorse struck down by lightning”, Mecedon Ranges Leader,14 November 2008).

These few examples were given to emphasize the gravityof the situation that, as all other incidents discussed in thispaper, they may have incurred similar or heavier losses tothe respective animal owners.

The analysis given in many research papers discussedearlier shows clear evidence that even when animals surviveafter step-potential and near-lightning effects, most oftentheir commercial values are either lost or degraded due tovarious post-event disabilities.

Safety procedures

It is difficult to prevent animals that graze in herds in largefields from being subjected to lightning effects. Accordingto the reports on mass deaths of animals in farms (such as incases 16, 21 and 22), they were most often in open mountain

tops or slopes, underneath large trees or close to metallicfences during the time of occurrence of lightning. Animalsaffected in large numbers, while they were grazing in flat,low terrains are rare compared with similar fields in highlyelevated or sloped locations. The low probability of light-ning to such flat terrains (compared to the probability ofstriking to surrounding mountains) and the high content ofmoisture in low-lying fields (that reduces the surface soilresistivity) may be the reasons for these observations. There-fore, if the movement of herds can be controlled, thereshould be a mechanism to lead the herd away from moun-tain tops and open slopes towards flat terrains in thelowlands.

As we have discussed earlier, it is a natural behavior ofherding animals to move towards fences or take shelterunder trees as a storm approaches. Hence, there should bea preventive mechanism of animals approaching the metalfences and large trees during thunderstorm activities. How-ever, in most of the cases such preventive mechanisms arenot practically feasible.

In the case of fences with metal wires we propose thefollowing defenses:

1. The wires should be grounded at regular intervals; atleast at the supporting poles (which are usually placed3–5 m apart). This can be done by stapling a verticalwire together with horizontal wires at the pole. As thelightning current distributes along many parallel pathseach wire can have a minimum cross section of about 6–8 mm2 (diameter of about 1.5 mm). Most barbed wiresavailable in the market are suitable for this purpose.

2. If the fence encloses the animal field, then an additionalround of wires should be buried about 50 cm beneaththe ground surface (IEC 62305-3 2006). This is termeda ring conductor. The vertical wires at the poles shouldbe connected to the ring conductor at the depth of50 cm. The connection should better be done withexothermic or thermo welding. If such welding incurstoo high a cost, then the vertical wire should be twistedwith the ring conductor at least for 20 cm.

3. If the fence is open ended (not completely encircling theanimal field) then, in addition to the procedures given inpart b, it is advisable to have a wire, extending for about3–4 meters outwards from the ring conductor at regularintervals (at the points that the vertical wires areconnected to the ring conductor). The connection ofthese extensions should be done in the same way asthe vertical wire is connected to the ring conductor.

4. A strip of about 2 m of ground surface from the fence(inside the animal field) should be covered with a 10–20 cm layer of gravel or any other earth material that hasan extremely high resistivity. This is a common practicein electrical switchyards that prevents workers from



being electrocuted due to undesirable earth fault cur-rents that may flow accidentally. The width of the stripmay be adjusted so that it is slightly larger than the spanof front and rear legs of the animal (2 m is most oftensufficient for cattle farms).

5. If the fence is made on a concrete foundation andvertical metal poles, the poles should be welded to thesteel reinforcement during the construction. The wiresshould be tightly stapled (if not welded) to the poles.The procedure described in part 4 should be imple-mented in this case as well.

6. In the case of fences with wooden poles and metalwires, it is advisable to check the condition of the buriedparts at most once in 5 years and do the necessaryreplacement before the thunderstorm season begins. Inregions where the salinity of the soil is high (coastalsites) the inspection needs to be done more frequently.

In many animal farms or kraals it is a common site tohave a solitary tree with large span of branch shade. The treeprovides the needed shade for the animals during hot day-time. However, the same tree may bring death to the animalduring thunderstorms. If there is no mechanism to avoid theanimals taking shelter under these trees during thunder-storms it is advisable to cover the ground surface (at leastthe part of ground underneath the branch span) with a 10–20 cm layer of gravel or any other earth material that hasextremely high resistivity. The greater the area of coveragewith gravel, the better the safety of the animals. Furthermore,the following procedures are also proposed to reduce thepossibility of side flashes (refer to Fig. 6):

1. A metal wire ring (wire of cross section about 8 mm2)should be installed around the tree trunk at about 3 mabove ground level. Most of the barbed wires availablein the market satisfy this condition. The spikes of thebarbed wires should be removed before the installation.

2. Connect 3–4 wires with similar cross section, each oflength about 10 m, to the ring at nearly equal spacing.

3. The wires should be extended vertically down towardsthe base of the tree.

4. Tie up the vertical wires by metal wire rings at abouteach 1 m interval. These tie rings can be made similar tothe metal wire ring described in part 1.

5. At the base of the tree, wires should be buried at about50 cm below the ground level and extended radiallyaway (for about 6–7 m).

6. The above steps should be carried out before the area isfilled with gravel. It is advisable to cover at least theentire area of buried wires with gravel (and extend a fewmore meters if the cost permits).

In contrast to the agricultural animals herded in largefields, animals in captivity or domesticated animals, whichhave greater chances of being inside shelters, can be betterprotected. Mainly, stallions, elephants and animals in zoo-logical gardens fall into this category.

Among the domesticated/tamed animals, elephants havea higher risk of getting injured or being killed due to light-ning as they may be subject to step potentials, touch poten-tials and side flashes. The situation can be even worse if theelephants are tied to large trees or stumps with metal chains.As the elephant is quite tall it may get a side flash when thetree is struck by lightning. In this case the lightning maymost probably jump to the head of the animal from the tree,killing it on the spot. Even if it escapes from a side flash thelightning current may automatically be brought into hisbody by the metal chain. Another way of elephants receivinga dose of lightning current when it is underneath a tree isthrough touch potential as it was described earlier.

A special place should be prepared to tie up these animalsunder thunderstorm conditions. They should never be tiedup to large isolated trees. The area, within which the animalis allowed to move, should be laid with a mesh of copper

Fig. 6 The proposed safety mechanism to protect animals that seekshelter under isolated trees in the field Fig. 7 The proposed safety mechanism to protect captive animals



strips (of minimum cross sectional area 8 mm2) underneaththe ground surface. As copper is costly, GI pipes, GI tapes,barbed wire, etc., can also be used for the purpose. Forelephants, a mesh of maximum dimensions 3 m×3 m issuitable whereas for horses, donkeys and cattle it should beless than 2 m×2 m. The mesh should be buried about 0.5 mbelow the ground level. Four metal poles should be installedand well grounded at the ends of the area (to have an earthresistance of less than 10 Ω). GI pipes of about 2.5-cmdiameter and 3-mm thickness will be adequate for the pur-pose. The metal mesh should firmly be joined to the ground-ing of the metal poles (better to be thermo welded). Thereshould be a facility to connect electrically the chain of theelephant to the grounding system, which is an essential partof the protection system. If a low cost option is adoptedinstead of copper, then it is advisable to inspect the condi-tion of the underground mesh at least in every two years.Figure 7 shows a diagram of such protection scheme. Thecalculation has been done by assuming a protective angle of45° which is applicable to the protection of an object ofheight up to 10 m even at Level I protection (IEC 62305-32006).

The height of the poles above ground level (h) can bedecided according to the formula below. Let the height ofthe animal be x.

For rectangular areas with side lengths a and b, four poles

should be installed at the corners: h ¼ffiffiffiffiffiffiffiffiffiffiffiffia2þb2ð Þ

p2 þ x

For circular areas of radius r, four poles should be in-stalled at the ends of two perpendicular diameters; h0r+x,wherex can be taken as 3.5 m for elephants, 2.5 m for horsesand 2 m for donkeys, cattle, etc.

The cost of the above protection system will be muchsmaller than the value of these animals.

The elephants and other valuable animals should neverbe allowed to stay in open waters in thunderstorm condi-tions. This advice will be very valuable to the officials atelephant orphanages, elephant and horse owners, templeauthorities where elephants are housed and authorities ofzoological gardens. Another concern is the open performingarena of elephants, horses, bears, etc. at zoological gardensand circuses. These arenas should be given the above pro-tection even if the area is roofed. When the animals areprovided with shelter (such as elephant lodges, stables,etc.), the structure should be given the same protectionscheme.

Conclusions

Animal injuries and consequent permanent disabilities ordeath due to lightning related effects are not uncommon inmany parts of the world where the isokeraunic level is on the

higher side. Such situation demands comprehensive analysisof lightning-caused injury mechanisms with the view ofdeveloping protection schemes for the animal safety againstlightning hazards.

Many of the lightning injury mechanisms of the animalsare similar to those of human beings. However, the effec-tiveness of each mechanism in affecting the body organs andthe exposure probabilities are somewhat different in the caseof animals. Step potential plays a vital role in the deaths of4-legged animals due to two reasons:

1. The large span between the feet2. The passage of sizable current through vital organs

irrespective of the direction of lightning strike (manyfoot combinations across which the current may flow).

In the case of tall animals such as elephants and giraffesside flashes and touch potential hazards are equally probableas the step potential effects.

Large herds of cattle and other domesticated animalshave been reported dead due to touch potentials as they resttheir parts of the body on ungrounded metal fences. Sideflashes and touch potential hazards of such animals arecommon as they gather around tall trees.

Low cost solutions are available to minimize the light-ning related injuries of animals. These techniques have beendiscussed in detail in the paper.

Acknowledgement The authors thankfully acknowledge the invalu-able information and materials provided by Mr. Randy Lantz, Ms.Jennifer Niemeyer and Prof. Diana Žele. The Department of Electricaland Electronics Engineering, Universiti Putra Malaysia is greatly ac-knowledged for providing all required facilities to complete this studysuccessfully.

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Lightning Safety of Animals

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