Are mixed diets beneficial for the welfare of captive axolotls (Ambystoma mexicanum)? Effects of feeding regimes on growth and behavior
Publication Type: |
Journal Article |
Year of Publication: |
2015 |
Authors: |
Dean J. Slight, Hazel J. Nichols, Kevin Arbuckle |
Publication/Journal: |
Journal of Veterinary Behavior: Clinical Applications and Research |
Keywords: |
activity, aquatic amphibian, development, environmental enrichment, folklore husbandry, nutrition |
ISBN: |
1558-7878 |
Abstract:
Good nutritional husbandry is crucial to maintain high welfare standards in captive animals. Both direct effects of diet on growth, development, and maintenance and indirect effects of feeding regimes on behavior may be important. Despite this, many questions remain as to how we should best feed many of the species that are commonly kept in captivity. There is a great deal of speculation among animal keepers as to issues such as whether a mixed diet is better than an invariant one, but little research is available to inform this question. In this study, we investigate the impact of mixed versus invariant diets on growth and behavior in the axolotl (Ambystoma mexicanum), an aquatic amphibian of severe conservation concern that is frequently maintained in captive collections. We then use our results to provide advice on feeding management in the context of improved welfare. We maintained juvenile axolotls under 1 of 3 “diets” (feeding regimes): bloodworm (invariant), Daphnia (invariant), and alternating these 2 prey items between feeds (mixed). Morphologic and behavioral data were collected over a period of 15 weeks and analyzed using generalized linear mixed models to determine whether our feeding treatments influenced growth and behavior. We find that axolotls grew fastest on our bloodworm diet and slowest on our Daphnia diet, with a mixed feeding regime leading to intermediate growth rates. Diet treatment did not significantly influence our measured behaviors, but feeding and locomotion events were more frequent (and resting less frequent) on feeding days than nonfeeding days. These data suggest that providing a mixed diet is not necessarily beneficial to either growth or welfare of captive animals. In the case of axolotls, an invariant diet of bloodworm should increase growth rates, but the diet (mixed vs. invariant) does not influence behavior. Overall, our results suggest that mixed diets in themselves may not be beneficial to the growth or welfare of axolotls as compared with a high-quality invariant diet.