Cannibalism in Chalarodon madagascariensis (Squamata: Iguanidae
2
Cannibalism or intraspecific predation, the killing and consumption of conspecifics, is a behavioural trait common to a range of taxa (Fox, 1975), having been recorded in over 1300 species in diverse taxonomic groups ranging from protozoa to mammals (Polis, 1981). The behaviour is widespread amongst reptiles and amphibians, and had been recorded in more than 100 species by 1985 (Polis and Myers, 1985). Here we report an observation of cannibalism in the iguanid lizard Chalarodon madagascariensis Peters, 1854. This endemic genus is currently recognised as monotypic (although unrecognised cryptic diversity exists, Münchenberg et al., 2008), and is largely restricted to the dry regions of southern and western Madagascar (Glaw and Vences, 2007). The species is terrestrial and inhabits areas with a sandy substrate, which is required for nesting (Blanc, 1970). Little is known about its diet, though Brillet (1982) reports that it eats ants, small flowers and, where it occurs by the coast, small intertidal crustaceans. On 24.04.2011 at 12.28, we were surveying birds on coastal sand dunes adjacent to the mangroves of Ambondrolava (23.262° S, 43.617° E), 10 km north of the regional capital Toliara in southwest Madagascar. Alerted by rustling within the sparse vegetation cover, we observed and photographed an adult C. madagascariensis predating a conspecific juvenile (Fig. 1). We did not observe the capture, but found the animals when the prey item had already been partially ingested, with only the hind legs and tail protruding from the predator’s mouth. The prey item was identified as C. madagascariensis based on the structure of the feet and colouration of the hind legs and tail base. It was assumed to be a juvenile on the basis of relative size (compared to the predator) and the poor development of scalation on the tail. After several seconds of observation, the predator fled into the vegetation and was not relocated. Polis and Myers (1985) suggest that cannibalism represents a normal part of feeding behaviour in many reptiles, because conspecifics form a low but constant proportion of dietary items, implying that they are treated as any other prey. Since recorded prey items comprised young animals in the majority of reptile taxa, Polis and Myers (1985) hypothesise that cannibalism may be the product of opportunistic capture in such species. They go on to propose that the incidence of cannibalism may be increased by environmental or nutritional stress, or a rise in population density (particularly of juveniles). Our observation appears to conform to this hypothesis; the event was observed at the end of the rainy season, during which the species breeds (Blanc, 1969), implying an elevated density of juveniles. Furthermore, the site where the observation occurred is characterised by very sparse vegetation, composed primarily of annual and perennial herbs. This may represent marginal habitat with low food availability, thereby increasing the probability of intraspecific predation as a result of nutritional stress. We are not aware of records of cannibalism in other Malagasy reptile species, including other iguanid species such as the well-studied Oplurus cuvieri (H. Randriamahazo pers. comm.). Acknowledgements. We would like to thank Richard Griffiths and Raul Fernandes Dantas de Sales for the provision of literature, Herilala Randriamahazo for information on Oplurus cuvieri, and Zoe Davies and Frank Glaw for comments which helped improve the quality of the manuscript. Herpetology Notes, volume 5: 127-128 (2012) (published online on 25 April 2012) Cannibalism in Chalarodon madagascariensis (Squamata: Iguanidae) from southwest Madagascar Charlie Gardner* 1 and Louise Jasper 2 1 Durrell Institute of Conservation and Ecology, University of Kent, Canterbury, Kent, CT2 7NS, UK, and WWF Madagas- car and Western Indian Ocean Programme Office, BP 738, Antananarivo 101, Madagascar; e-mail: [email protected] 2 BP 639, Toliara 601, Madagascar; e-mail: [email protected] * corresponding author
Transcript of Cannibalism in Chalarodon madagascariensis (Squamata: Iguanidae
Cannibalism or intraspecific predation, the killing and consumption of conspecifics, is a behavioural trait common to a range of taxa (Fox, 1975), having been recorded in over 1300 species in diverse taxonomic groups ranging from protozoa to mammals (Polis, 1981). The behaviour is widespread amongst reptiles and amphibians, and had been recorded in more than 100 species by 1985 (Polis and Myers, 1985). Here we report an observation of cannibalism in the iguanid lizard Chalarodon madagascariensis Peters, 1854. This endemic genus is currently recognised as monotypic (although unrecognised cryptic diversity exists, Münchenberg et al., 2008), and is largely restricted to the dry regions of southern and western Madagascar (Glaw and Vences, 2007). The species is terrestrial and inhabits areas with a sandy substrate, which is required for nesting (Blanc, 1970). Little is known about its diet, though Brillet (1982) reports that it eats ants, small flowers and, where it occurs by the coast, small intertidal crustaceans.
On 24.04.2011 at 12.28, we were surveying birds on coastal sand dunes adjacent to the mangroves of Ambondrolava (23.262° S, 43.617° E), 10 km north of the regional capital Toliara in southwest Madagascar. Alerted by rustling within the sparse vegetation cover, we observed and photographed an adult C. madagascariensis predating a conspecific juvenile (Fig. 1). We did not observe the capture, but found the animals when the prey item had already been partially ingested, with only the hind legs and tail protruding from the
predator’s mouth. The prey item was identified as C. madagascariensis based on the structure of the feet and colouration of the hind legs and tail base. It was assumed to be a juvenile on the basis of relative size (compared to the predator) and the poor development of scalation on the tail. After several seconds of observation, the predator fled into the vegetation and was not relocated.
Polis and Myers (1985) suggest that cannibalism represents a normal part of feeding behaviour in many reptiles, because conspecifics form a low but constant proportion of dietary items, implying that they are treated as any other prey. Since recorded prey items comprised young animals in the majority of reptile taxa, Polis and Myers (1985) hypothesise that cannibalism may be the product of opportunistic capture in such species. They go on to propose that the incidence of cannibalism may be increased by environmental or nutritional stress, or a rise in population density (particularly of juveniles). Our observation appears to conform to this hypothesis; the event was observed at the end of the rainy season, during which the species breeds (Blanc, 1969), implying an elevated density of juveniles. Furthermore, the site where the observation occurred is characterised by very sparse vegetation, composed primarily of annual and perennial herbs. This may represent marginal habitat with low food availability, thereby increasing the probability of intraspecific predation as a result of nutritional stress.
We are not aware of records of cannibalism in other Malagasy reptile species, including other iguanid species such as the well-studied Oplurus cuvieri (H. Randriamahazo pers. comm.).
Acknowledgements. We would like to thank Richard Griffiths and Raul Fernandes Dantas de Sales for the provision of literature, Herilala Randriamahazo for information on Oplurus cuvieri, and Zoe Davies and Frank Glaw for comments which helped improve the quality of the manuscript.
Herpetology Notes, volume 5: 127-128 (2012) (published online on 25 April 2012)
Cannibalism in Chalarodon madagascariensis (Squamata: Iguanidae) from southwest Madagascar
Charlie Gardner*1and Louise Jasper2
1 Durrell Institute of Conservation and Ecology, University of Kent, Canterbury, Kent, CT2 7NS, UK, and WWF Madagas-car and Western Indian Ocean Programme Office, BP 738, Antananarivo 101, Madagascar;
e-mail: [email protected] BP 639, Toliara 601, Madagascar; e-mail: [email protected]* corresponding author
Charlie Gardner & Louise Jasper 128
References
Blanc, C.P. (1969): Etudes sur les Iguanidae de Madagascar II. Observations sur l’écologie de Chalarodon madagascariensis Peters, 1854. Oecologia 2: 292-318.
Blanc, C.P. (1970): Analyse des facteurs de l’environnement dans l’aire de répartition de Chalarodon madagascariensis: leurs implications biologiques. Annales de l’Université de Madagas-car: série Sciences de la Nature et Mathématiques 7: 279-306.
Brillet, C. (1982): Contribution à l’étude des relations entre indi-vidus chez cinq espèces d’iguanes malgaches du genre Oplur-us. Rev. Ecol.-Terre Vie 36: 79-148.
Fox, L.R. (1975): Cannibalism in natural populations. Ann. Rev. Ecol. Syst. 6: 87-106.
Glaw, F., Vences, M. (2007): A Field Guide to the Amphibians and Reptiles of Madagascar, 3rd Edition. Köln, Vences and Glaw Verlags GbR.
Münchenberg, T., Wollenberg, K.C., Glaw, F., Vences, M. (2008): Molecular phylogeny and geographic variation of Malagasy iguanas (Oplurus and Chalarodon). Amph.-Rept. 29: 319-327.
Polis, G.A. (1981): The evolution and dynamics of intraspecific predation. Ann. Rev. Ecol. Syst. 12: 225-251.
Polis, G.A., Myers, C.A. (1985): A survey of intraspecific predati-on among reptiles and amphibians. J. Herpetol. 19: 99-107.
Figure 1. Adult Chalarodon madagascariensis with partially ingested conspecific juvenile.
Accepted by Zoltan T. Nagy
