# Long-term impacts of captivity on skull morphology and endocranial volume in a marsupial carnivore

## TL;DR

Captive breeding in a marsupial carnivore leads to skull and brain changes that may affect survival when released into the wild.

## Contribution

This study is the first to document morphological and endocranial changes in a marsupial due to long-term captivity.

## Key findings

- Captive dunnarts had brachycephalic skulls with shorter molar lengths and broader zygomatic widths.
- Captive individuals had a 3.8% larger endocranial volume compared to wild individuals.
- These changes may impact dietary, cognitive, and sensory functions, affecting survival in the wild.

## Abstract

A challenge in modern conservation is maintaining ecological roles and natural behaviours of wildlife in an anthropogenic world. Captive breeding has been linked to morphological changes that may impact individual fitness for reintroduction to the wild. Changes in skull morphology and brain size may be linked to functional and behavioural changes, influencing survival outcomes. These issues have been explored in numerous eutherian mammals, but rarely in metatherians. We compared skull morphology and endocranial volume in a carnivorous marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata), between wild-derived and captive individuals maintained in a university laboratory colony over tens of generations. Skulls from captive dunnarts were brachycephalic, with significantly shorter basal and upper molar lengths, broader zygomatic widths and longer palate and toothrow lengths, compared with wild counterparts. Captive-bred dunnarts also had a mean endocranial volume 3.8% larger than wild individuals. These traits relate to dietary, cognitive and sensory capabilities and can be linked to functional differences within captive and wild populations. Therefore, changes to these regions could have substantial fitness consequences in natural habitats. By addressing the ways laboratory management can influence morphological traits, we can reassess broader captive management techniques to improve the success of future breeding and reintroduction programmes.