Optimal husbandry of hatchling Eastern Indigo Snakes (Drymarchon couperi) during a captive head-start program

Abstract

Optimal husbandry techniques are desirable for any headstart program, but frequently are unknown for rare species. Here we describe key reproductive variables and determine optimal incubation temperature and diet diversity for Eastern Indigo Snakes (Drymarchon couperi) grown in laboratory settings. Optimal incubation temperature was estimated from two variables dependent on temperature, shell dimpling, a surrogate for death from fungal infection, and deviation of an egg from an ovoid shape, a surrogate for death from developmental anomalies. Based on these relationships and size at hatching we determined optimal incubation temperature to be 26°C. Additionally, we used incubation data to assess the effect of temperature on duration of incubation and size of hatchlings. We also examined hatchling diets necessary to achieve optimal growth over a 21-month period. These snakes exhibited a positive linear relationship between total mass eaten and growth rate, when individuals were fed less than 1711 g of prey, and displayed constant growth for individuals exceeding 1711 g of prey. Similarly, growth rate increased linearly with increasing diet diversity up to a moderately diverse diet, followed by constant growth for higher levels of diet diversity. Of the two components of diet diversity, diet evenness played a stronger role than diet richness in explaining variance in hatchling growth. These patterns document that our goal of satiating snakes was achieved for some individuals but not others and that diets in which total grams consumed over the first 21 months of life is distributed equivalently among at least three prey genera yielded the fastest growth rates for hatchling snakes.

Tradeoffs with Growth and Behavior for Captive Box Turtles Head-Started with Environmental Enrichment

“…Head-starting, a practice that involves captive-rearing animals for release into nature, is a popular approach for augmenting or reintroducing imperiled wildlife populations. A common focus in these programs involves rapidly growing individuals to reduce susceptibility to predation or be closer to reproductive age or size upon release [1][2][3]. However, emphasis on rapid growth may have undesirable consequences, such as the degradation or loss of normal behaviors.…”

Modeling strategies and evaluating success during repatriations of elusive and endangered species

“…; Supporting Information Appendix ). We modeled productivity (fecundity; F ) with a mean of 8.6 eggs per female with a Poisson‐distributed random variable for all breeding stages, but we modeled the proportion of viable eggs, P (ve), as less for primiparous females [ P (ve) PA = 0.35; 0.05 se ] than adult females [ P (ve) A = 0.85; 0.05 se ; Wines et al , ]. Our productivity parameters assume that fecundity of released individuals will operate similarly to what we have observed among wild‐caught and captive‐raised females.…”