# Springing into action: Comparing escape responses between bipedal and quadrupedal rodents

## TL;DR

Bipedal rodents like kangaroo rats escape predators better through vertical jumps compared to quadrupedal rodents.

## Contribution

This study is the first to directly compare escape performance between bipedal and quadrupedal rodents using simulated predator attacks.

## Key findings

- Bipedal kangaroo rats and pocket mice showed similar jumping performance, likely due to shared anatomical traits.
- Quadrupedal woodrats and ground squirrels rarely jumped and had slower escape responses compared to bipedal rodents.
- Take-off velocity was the only significant difference in jump performance among bipedal species.

## Abstract

Predation is a fundamental selective pressure on animal morphology, as morphology is directly linked with physical performance and evasion. Bipedal heteromyid rodents, which are characterized by unique morphological traits such as enlarged hindlimbs, appear to be more successful than sympatric quadrupedal rodents at escaping predators such as snakes and owls, but no studies have directly compared the escape performance of bipedal and quadrupedal rodents. We used simulated predator attacks to compare the evasive jumping ability of bipedal kangaroo rats (Dipodomys) to that of three quadrupedal rodent groups—pocket mice (Chaetodipus), woodrats (Neotoma), and ground squirrels (Otospermophilus). Jumping performance of pocket mice was remarkably similar to that of kangaroo rats, which may be driven by their shared anatomical features (such as enlarged hindlimb muscles) and facilitated by their relatively small body size. Woodrats and ground squirrels, in contrast, almost never jumped as a startle response, and they took longer to perform evasive escape maneuvers than the heteromyid species (kangaroo rats and pocket mice). Among the heteromyids, take‐off velocity was the only jump performance metric that differed significantly between species. These results support the idea that bipedal body plans facilitate vertical leaping in larger‐bodied rodents as a means of predator escape and that vertical leaping likely translates to better evasion success.

The findings of this study suggest that enlarged hindlimbs improve escape performance by allowing rodents to more efficiently utilize vertical jumping as an antipredator escape response.