Study shows that marsupial gliders may avoid predators by staying off the ground

Bats, the only mammals capable of flight, set themselves apart from other mammals that can glide through the air, like certain squirrels and lemurs. These gliding mammals navigate using membranes stretched between their limbs, prompting scientists to ponder the evolutionary reasons behind this aerial adaptation. Recent research suggests that some mammals opt for gliding as a strategy to evade ground-based predators.

According to ecologist Jasmin Annett from the University of the Sunshine Coast in Sippy Downs, Australia, the ability to glide has independently evolved at least nine times among mammals. While gliding is predominantly seen in a single family of marsupials, exemplified by the endangered mahogany glider (Petaurus gracilis), studying these nocturnal creatures remains challenging.

Annett’s team conducted a behavior analysis on two captive mahogany gliders alongside four brushtail possums (Trichosurus vulpecula), closely related variety that lack the gliding adaptation.

To glean insights into the function of gliding within the animal kingdom, the researchers captured wild brushtail possums, employing a tempting tactic of using peanut butter sandwiches as bait. Annett remarks, “They love them.”

The study involved equipping the animals with motion sensor-laden collars or cat harnesses to monitor changes in speed and direction, correlating these data with observed behaviors like climbing, eating, and resting.

By employing a machine learning algorithm to analyze matched sets of behaviors and motion sensor data, the researchers identified distinguishing animal behaviors during hundreds of hours of sensor data collection for each species.

Comparative analysis reveals that mahogany gliders expend higher energy levels in locomotion compared to brushtail possums, with distinct activity peaks throughout the day and a preference for occupying elevated areas in their enclosures.

These findings suggest that gliding in marsupials may have evolved as a defense mechanism against ground-dwelling predators, as elucidated in the team’s report published on November 28 in the Journal of Zoology.

Future investigations aim to contrast the behaviors of other non-gliding marsupials like the ringtail possum, a species that exhibits more arboreal tendencies than its brushtail possum relative.

Unlocking Gliding Behaviors

Researchers monitored the activity levels of two marsupial species: mahogany gliders (dark blue) and brushtail possums (light blue), gauging their energy expenditure hourly. Utilizing sensors to track movement, the team trained a machine learning algorithm to recognize distinct behavioral patterns in brushtail possums (Figure 2a) and mahogany gliders (Figure 2b). Explore the full-scale versions of each figure by clicking on the images.

two pi charts showing how often mahogany gliders and brushtail possums spent doing various activities
Both: J.R. Annett et al/Journal of Zoology 2023; adapted by L. Steenblik Hwang

In-Depth Analysis:

  1. Examining Figure 1, what can be deduced about the activity patterns of brushtail possums throughout the 24-hour day? Are they diurnal or nocturnal?
  2. When did mahogany gliders exhibit peak activity levels? How do their activity patterns differ from those of brushtail possums?
  3. Reviewing Figure 2, what activities consumed the majority of brushtail possums’ time?
  4. Which activities accounted for the most time in the routine of mahogany gliders?
  5. What percentage of time did brushtail possums spend engaging in ground-based activities compared to mahogany gliders?
  6. Another hypothesis posits that gliding enables animals to cover substantial distances swiftly. How could researchers investigate this notion further?

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