Short Communications 403

These experiments were all recently reviewed by Baerends (1985) together with data that I provided him with on my experiments which, however, were not then analysed statistically. A typographical error in my data as printed could be confusing. The total number of bites on red was given as 118, instead of 1118 (page 261). Also, I have added the last test for fish G in which red was bitten 36 times (Table I), raising the total for all fish from l 118 to 1 t 54 bites on red, compared with only 626 bites on the neutral model. Baerends found that the results of the different authors were often inconsistent and variable, and he suggested that the differences might be related particularly to differences in control of the escape factor.

I tried to minimize the escape factor by not moving the model during tests and also by placing the model fairly close (usually about 10 cm) to the nest as the territorial centre. Others (van Iersel 1958; Huntingford 1977; Rowland 1983) have found that the frequency of attacks on a male enclosed in a glass tube or flask declines with increasing distance from the nest. My data pro- vide statistically significant evidence, apparently hitherto lacking, that close to the territorial centre represented by the nest, the male resident is more likely to attack an intruder with a red belly than one with a grey belly. But especially when near or just beyond the borders of his territory, the male may often be intimidated by red. Recently, Rowland & Sevenster (1985) used stationary red-bellied versus uniformly silver models presented simultaneously in pairs at 30 cm from the test male's nest, and both New York and Dutch males attacked the silver dummy significantly more than the red one.

In conclusion, the red belly of a breeding male three-spined stickleback not only excites aggression, but also has an intimidatory function (Tinbergen 1948; Woot ton 1976; Rowland & Sevenster 1985). In addition, the red belly helps identify the male as such to the female. In the most general terms, as Tinbergen (1948) stated, the red coloration of the male three-spined stickleback serves as a social signal indicating the presence of a male in breeding condition with a nest and a territory. In the future, tests would be desirable in which the lightness or darkness of a grey belly was varied systematically in models and matched against red to test the importance of colour per se.

I am greatly indebted to the late Niko Tinbergen for his many kindnesses and generosity when I was a guest in his laboratory at the University of Leiden. J. J. A. van Iersel was of the greatest assistence with both practical matters and friendly advice, and I wish to dedicate this article to him on the occasion of his retirement from the Univeristy of Leiden. I thank Professor W. J. Dixon of the Biomathematics

Department at the University of California for helpful advice on appropriate statistical techniques. Elsie Collias, W. J. Rowland and P. Colgan made useful comments on the manuscript.

NICHOLAS E. COLLIAS Department o f Zoology, University o f California, Los Angeles, CA 90024, U.S.A.

References

Baerends, G. P. 1985. Do the dummy experiments with sticklebacks support the IRM-concept? Behaviour, 93, 259 277.

Dixon, W. J. & Massey, F. J., Jr. 1983. Introduction to StatisticalAnalysis'. 4th edn. New York: McGraw-Hill.

Huntingford, F. A. 1977. Inter- and intraspecific aggression in male sticklebacks. Copeia, 1977, 158-159.

van Isersel, J. J. A. 1953. An analysis of the parental behav- iour of the male three-spined stickleback (Gasterosteus aculeatus L.). Behaviour, Suppl., 3, 1-159.

van Isersel, J. J. A. 1958. Some aspects of territorial behaviour of the male three-spined stickleback. Archs n~erl. Zool. Suppl., 1,383-400.

Peeke, H. V. S., Wyers, E. J. & Herz, M. J. 1969. Waning of the aggressive response to male models in the three- spined stickleback (Gasterosteus aculeatus L.). Anita. Behav., 17, 224~228.

ter Pelkwijk, J. J. & Tinbergen, N. 1937. Eine reiz- biologische Analyse einiger Verhaltensweisen von Gasterosteus aculeatus L. Z. Tierpsychol., 1,103-200.

Rowland, W. J. 1983. Interspecific aggression in stickle- backs: Gasterosteus aculeatus displaces Apeltes quadracus. Copeia, 1983, 541-544.

Rowland, W. J. & Sevenster, P. 1985. Sign stimuli in the threespine stickleback (Gasterosteus aculeatus): a re-examination and extension of some classic experiments. Behaviour, 93, 241-257.

Sevenster, P. 1961. A causal analysis of a displace- ment activity (fanning in Gasterosteus aculeatus L.). Behaviour, Suppl., 9, 1-170.

Tinbergen, N. 1948. Social releasers and the experimental method required for their study. Wilson Bull., 60, (~51.

Wootton, R. J. 1976. The Biology of the Sticklebacks. London: Academic Press.

(Received 13 June 1989; initial acceptance 27 June 1989; final acceptance 17 July 1989;

MS. number: AS-633)

Sandbathing Reduces Fur Lipids of Chinchillas, Chinchilla laniger

Sandbathing behaviour is understood to function in the care of the body surface. Rodents adapted to arid environments exhibit increased productivity of the sebaceous glands. When such animals are deprived of access to sand suitable for dressing the pelage,

404 Animal Behaviour, 39, 2

their coat becomes matted and greasy-looking. Access to sand produces a rapid improvement in appearance of the fur (Eisenberg 1963; Borchelt et al. 1976). Pelage lipid-reduction thus appears to be a primary consequence of sand-bathing. Griswold et al. (1977) found that experimental application of lanolin to the fur of kangaroo rats, Dipodomys merriami, increased the number of sandbathing rubs directed to the treated surface (but not to non- treated surfaces) and interpreted the result as supporting a regulatory effect of pelage lipids with respect to sandbathing behaviour and vice versa.

Although the view that sandbathing reduces pelage lipid may be reasonable, there are little hard data on the point. The one study that has looked at the effect of living on a sand substrate on pelage lipids does not provide strong support for the lipid- reduction view. Thiessen & Pendergrass (1985) measured the changes in pelage lipids of Mongolian gerbils during prolonged exposure to sand. Gerbils were exposed either to a sand substrate or to a wire- mesh substrate suspended above (and out of reach of) sand. Fur lipids were measured after 2, 8 or 16 days. At 8 days, fur lipids were elevated in the mesh- substrate group but were unchanged in gerbils on the sand. At 16 days, fur lipids of the animals exposed to sand had decreased significantly to approximately two-thirds of their level at 8 days. These results seem inconsistent with reports that fur lipids of kangaroo rats were visibly reduced during a single sandbathing bout (Borchelt et al. 1976) but the existence of the Harderian gland as a major source of additional lipid in the gerbil may be a confounding factor (see Thiessen & Kittrell 1980).

In our study, 16 adult chinchillas (eight male, eight female) were shampooed (three applications of approximately 8 ml &Johnson's baby shampoo) to produce a uniform initial condition of the pelage, maintained on a steel mesh floor and deprived of sand for 25 days to allow for lipid accumulation, given 1 day of continuous access to sand (Attapulgus clay, 50/80 RVM, Engelhard Minerals and Chemi- cals Division, Edison, New Jersey) in the home cage, and then shampooed (as described above) a second time. Each subject provided three fur samples, one following 25 days of sand deprivation, one following 24 h access to sand, and one a day after the final shampooing. Fur samples were taken, using hair shears, from standard rectangles measuring 25 x 64 mm to the left and right of the dorsal midline. Rostro-caudal position of sampling rectangles was counterbalanced across animals and conditions so as to prevent bias attributable to possible systematic variation in fur lipid with body location. Disposable plastic gloves were worn when handling the animals.

Lipids were extracted from fur samples by means of a 24-h soak in 20 ml chloroform-methanol (2:1, by volume) followed by rinsing in a second 20 ml of the solvent. The solvent with extract was filtered (using Whatman no. 2 paper), washed by shaking with a 0.88% solution of potassium chloride in dis- tilled water to remove non-lipids (Christie 1973), separated from the aqueous phase and placed in a tared beaker, and the solvent evaporated under an evaporation hood (48 h). Fur was dried under the same hood. Beakers were reweighed and results were expressed as mg lipid per g of defatted fur (Table I).

Table I. Pelage lipids extracted (mg/g fur + SE) following successive manipulations

After After After 25 days sand 24 h access final deprivation to sand shampoo

Males 113+ 6 80+ 4 8l__+ 8 (N=8) Females 116_+15 924-11 794-10 (U = 8)

Data were analysed by means of repeated- measures ANOVA with sex as a between-subjects factor. The effect of experimental treatments was highly significant ( F = 24.19, df=2,28, P < 0.001). Sex did not affect pelage lipid level and there was no sex by treatment interaction. Post-hoc tests (Newman-Keuls, P <0-05) showed that there was no difference between the last two tests (following sand and shampoo, respectively) but that both were significantly lower than the first (following sand deprivation).

The data indicate that fur lipids remaining after the 24-h access to sand were not reduced further by subsequent shampooing. The greater effectiveness of sandbathing for males, 29% lipid removal versus 21%0 for females, although not statistically signifi- cant, is consistent with the fact that males in this sample exhibited greater frequency of rolling in sand (unpublished data).

I f post-sandbathing measures are taken as an indicator of natural lipid levels in the fur, then the extracted hair fats constitute approximately 8% of total fur weight. This compares with values of about 2% for rats (Ebling & Skinner 1967) and 2- 16% for various breeds of sheep (Truter 1956), although strict comparability of results is hampered by procedural differences.

Access to sand for 1 day may reduce lipid content of chinchilla fur. Thiessen & Pendergrass (1985)

Short Communications 405

found that 8-16 days of exposure to a sand sub- strate were necessary to effect lipid reduction in Mongolian gerbils. Thiessen & Pendergrass suggested passive absorbence of hair fat by the sand substrate as a prominent factor. A similar expla- nation could be offered for the present data but this is not consistent with the relatively short time period in which lipid reduction was effected in chinchillas compared to gerbils. We suggest as other potentially important variables: differences in the frequency, topography, or vigour of sandbathing by gerbils and chinchillas; differences in the absorbence of the type of sand used; species difference in the lipid types and distribution mechanisms; differences in the initial level of fur lipids; or simply procedural differences in the lipid analyses and experimental treatments.

We thank the Biology Department of Hunter College, Victoria Luine and Marcia Brody for advice and equipment for the lipid analyses. This experiment constituted part of the Ph.D. thesis research of N.B. in the laboratory of R.L.T. and was supported by funds from the Biopsychology Program at Hunter College.

NIGEL BARBER ROBERT L. THOMPSON

Department of Psychology, Hunter College, 695 Park A venue, New York, N Y 10021, U.S.A.

References

Borchelt, P. L., Griswold, J. G. & Branchek, R. S. 1976. An analysis of sandbathing and grooming in the kangaroo rat (Dipodomys merriami). Anim. Behav., 24, 347-353.

Christie, W. C. 1973. Lipid Analysis: Isolation, Separation, Identification and Structural Analysis of Lipids. Oxford: Pergamon Press.

Ebling, F. J. & Skinner, J. 1967. The measurement of sebum production in rats treated with testosterone and oestradiol. Br. J. Dermatol., 79, 386-393.

Eisenberg, J. F. 1963. A comparative study ofsandbathing behaviour in heteromyid rodents. Behaviour, 22, 16-23.

Griswold, J. G., Borchelt, P. L., Branchek, R. S. & Bensko, J. A. 1977. Condition of the pelage regulates sandbathing and grooming behaviour in the kangaroo rat (Dipodomys merriami). Anim. Behav., 25, 602-608.

Thiessen, D. D. & Kittrell, M. W. 1980 The Harderian gland and thermoregulation in the gerbil (Meriones unguiculatus). Physiol. Behav., 24, 417-424.

Thiessen, D. D. & Pendergrass, M. 1985. Change of pelage lipids in the Mongolian gerbil, Meriones unguiculatus, as the result of autogrooming and sandliving. J. Mammal., 6, 469-475.

Truter, E. V. 1956. Wool Wax: Chemistry and Technology. London: Cleaver-Hume.

(Received 26 June 1989; initial acceptance 27 June 1989; final acceptance 17 July 1989;

MS. number: AS-636)