Effects of food supplementation on the physiological ecology of female Western diamond-backed rattlesnakes (Crotalus atrox)

• Published in: Oecologia Vol. 144; no. 2; pp. 206 - 213
• Main Authors: Taylor, E.N, Malawy, M.A, Browning, D.M, Lemar, S.V, DeNardo, D.F
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01-06-2005; Springer Nature B.V
• Subjects: Amphibia. Reptilia; Analysis of Variance; Animal and plant ecology; Animal behavior; animal growth; Animal Nutritional Physiological Phenomena; animal physiology; Animal reproduction; Animal, plant and microbial ecology; Animals; Arizona; Biological and medical sciences; Birds; Body condition; Body Constitution; Body Weight; Crotalus - growth & development; Crotalus - physiology; Crotalus atrox; Dietary supplements; Eating - physiology; Ecophysiology; Female; Females; Field tests; Food availability; Food consumption; Food intake; Food resources; Food supply; Fundamental and applied biological sciences. Psychology; General aspects; Life history; Litter size; Motor Activity - physiology; Offspring; Physiological ecology; Physiology; Reproduction; Reproduction - physiology; Snakes; Trajectory control; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Arizona; Vertebrata; Reproduction; Energy; Growth; Snake; Female; Reptilia; Ecology; Supplementary feeding; Animal conservation; Ophidia
• DOI: 10.1007/s00442-005-0056-x
• EISSN: 1432-1939
• ISSN: 0029-8549

Food availability is an important factor in the life histories of organisms because it is often limiting and thus can affect growth, mass change, reproduction, and behaviors such as thermoregulation, locomotion, and mating. Experimental studies in natural settings allow researchers to examine the effects of food on these parameters while animals are free to behave naturally. The wide variation among organisms in energy demands and among environmental food resources suggest that responses to changes in food availability may vary among organisms. Since most supplemental feeding field experiments have been conducted on species with high energy demands, we conducted a supplemental feeding study on free-ranging, female Western diamond-backed rattlesnakes (Crotalus atrox), a species with low energy demands and infrequent reproductive investment. Snakes were offered thawed rodents 1-4 times per week. Over two active seasons, we collected data on surface activity, home range size, growth, mass change, and reproduction of supplementally fed and control snakes. Fed and control snakes did not differ in surface activity levels (proportion of time encountered above versus below ground) or home range size. Fed snakes grew and gained mass faster, and had a dramatically higher occurrence of reproduction than control snakes. Also, fed snakes were in better body condition following reproduction than snakes that were not fed. However, litter characteristics such as offspring number and size were not increased by feeding, suggesting that these characteristics may be fixed. These data experimentally demonstrate that food availability can directly impact some life history traits (i.e., growth and reproduction for C. atrox), but not others (i.e., surface activity and home range size for C. atrox). The relationship between food availability and life history traits is affected in a complex way by ecological traits and physiological constraints, and thus interspecific variation in this relationship is likely to be high.