Factors influencing the timing and frequency of litters in captive fennec foxes (Vulpes zerda).

Maintaining reproductive seasonality can be vital to the fitness of wild animals. Certain species, however, may display aseasonal reproduction and may produce multiple yearly litters when maintained in captivity. Wild fennec foxes (Vulpes zerda), for example, produce a single litter in March or April although their reproductive behaviors are reportedly variable in captivity. Here, we used the fennec fox studbook to extract traits related to reproductive variability in 220 captive-born litters. The captive litters in our dataset were born during every month of the year and nearly half (47%) were born outside of the expected months. The production of multiple litters in a single year was common, where 67% of the litters represented a second annual litter for a given dam. We detected several traits related to multi-litter years, including the dam's ability to habituate to the birth location, the dam's age, the dam's number of previous litters, and the dam's birth month. Although producing multiple litters within a year has been anecdotally associated with the loss of a previous litter, we did not detect a relationship between multi-litter years and the survivorship of previous litters. These findings suggest that captive populations of fennec foxes may experience a destabilization of their reproductive patterns, which may culminate in the production of multiple litters outside of the typical window of reproduction. Fennec foxes are a common captive species bred in zoos worldwide. Developing a greater understanding of their reproduction can allow for more successful captive management, which may improve future reproductive successes.

Endocranial volume increases across captive generations in the endangered Mexican wolf.

Endangered animals in captivity may display reduced brain sizes due to captive conditions and limited genetic diversity. Captive diets, for example, may differ in nutrition and texture, altering cranial musculature and alleviating constraints on cranial shape development. Changes in brain size are associated with biological fitness, which may limit reintroduction success. Little is known about how changes in brain size progress in highly managed carnivoran populations and whether such traits are retained among reintroduced populations. Here, we measured the endocranial volume of preserved Mexican wolf skulls across captive generations and between captive, wild, and reintroduced populations and assessed endocranial volume dependence on inbreeding and cranial musculature. Endocranial volume increased across captive generations. However, we did not detect a difference among captive, wild, and reintroduced groups, perhaps due to the variability across captive generations. We did not find a relationship between endocranial volume and either inbreeding or cranial musculature, although the captive population displayed an increase in the cross-sectional area of the masseter muscle. We hypothesize that the increase in endocranial volume observed across captive generations may be related to the high-quality nutrition provided in captivity.

Cranial morphology of captive mammals: a meta-analysis.

BACKGROUND: Captive facilities such as zoos are uniquely instrumental in conservation efforts. To fulfill their potential as bastions for conservation, zoos must preserve captive populations as appropriate proxies for their wild conspecifics; doing so will help to promote successful reintroduction efforts. Morphological changes within captive populations may be detrimental to the fitness of individual animals because these changes can influence functionality; thus, it is imperative to understand the breadth and depth of morphological changes occurring in captive populations. Here, we conduct a meta-analysis of scientific literature reporting comparisons of cranial measures between captive and wild populations of mammals. We investigate the pervasiveness of cranial differences and whether cranial morphological changes are associated with ecological covariates specific to individual species, such as trophic level, dietary breadth, and home range size. RESULTS: Cranial measures of skull length, skull width, and the ratio of skull length-to-width differed significantly between many captive and wild populations of mammals reported in the literature. Roughly half of captive populations differed from wild populations in at least one cranial measure, although the degree of changes varied. Carnivorous species with a limited dietary breadth displayed the most consistent changes associated with skull widening. Species with a more generalized diet displayed less morphological changes in captivity. CONCLUSIONS: Wild and captive populations of mammals differed in cranial morphology, but the nature and magnitude of their cranial differences varied considerably across taxa. Although changes in cranial morphology occur in captivity, specific changes cannot be generalized for all captive mammal populations. The nature of cranial changes in captivity may be specific to particular taxonomic groups; thus, it may be possible to establish expectations across smaller taxonomic units, or even disparate groups that utilize their cranial morphology in a similar way. Given that morphological changes occurring in captive environments like zoos have the potential to limit reintroduction success, our results call for a critical evaluation of current captive husbandry practices to prevent unnecessary morphological changes.

Stress and social behaviors of maternally deprived captive giraffes (Giraffa camelopardalis).

Maternal deprivation can cause long-term behavioral changes in captive mammals. Studies regarding captive ungulates have also indicated behavioral shifts in the presence of the animal keeping staff; however, little is known about these effects in captive giraffes (Giraffa camelopardalis). To examine this, we observed a population of reticulated giraffes composed of maternally raised and maternally deprived individuals by direct and camera observations at Binder Park Zoo, Battle Creek, Michigan. We conducted observations using a unique ethogram with special regard for behaviors that might indicate stress or anti-social tendencies. Several variables can interact to create behavioral changes; to account for this, our study design examined the interactive effects of observation technique, raising style, and temperature on giraffe behavior. The results of these observations showed a significant increase in the rate of stereotypic and antisocial behaviors resulting from the interaction of observation technique and raising style. Stereotypic behaviors in particular showed a marked increased during cooler temperatures among giraffes of all raising style. Likewise, raising style, observation technique, and their interaction significantly impacted the time spent rubbing the enclosure. The findings of this study suggest that captive giraffe behavior can be a complex response to multiple factors and studies only examining single factors might oversimplify behavioral shifts.