Captive Asian short-clawed otters (Aonyx cinereus) learn to exploit unfamiliar natural prey

Abstract

Foraging plays a vital role in animal life histories, and learning whether unfamiliar food items are palatable is a key part of this process. Animals that engage in extractive foraging must also learn how to overcome the protective measures of their prey. While otters (subfamily Lutrinae) are a taxon known for their extractive foraging behaviour, how they learn about prey palatability and acquire extractive foraging techniques remains poorly understood. Here we investigated (i) how captive Asian short-clawed otters (Aonyx cinereus) learned to interact with, and extract meat from, unfamiliar natural prey and (ii) how their exploitation of such prey compared to their ability to overcome artificial foraging tasks containing familiar food rewards. Network-based diffusion analysis showed that otters learned to interact with unfamiliar natural prey by observing their group mates. However, once interacting with the prey, they learned to extract the meat mainly asocially. In addition, otters took longer to overcome the protective measures of unfamiliar natural prey than those of extractive food puzzles. Asian short-clawed otter populations are declining in the wild. Increasing our understanding of how they learn to overcome novel foraging challenges could help develop pre-release training procedures as part of reintroduction programmes for otter conservation.

Keywords: extractive foraging; individual learning; network-based diffusion analysis; otters; problem-solving; social learning.

Figure 1.

The social transmission rates per unit network connection relative to the baseline rate of asocial learning, as estimated by (a) the top model of first prey interactions where social transmission rates were constrained to be different between the three natural prey types (black) and the top model where social transmission rates were constrained to be the same across the three natural prey types (grey), and (b) the top model analysing the time sequence in which otters extracted the meat from the prey types. Error bars indicate 95% confidence intervals. Social transmission rate estimates between models in the respective top sets were relatively similar (tables 2 and 3), and we have plotted these model estimates for illustration.

Figure 2.

The fitted extraction times from the best-supported extraction time model showing how the amount of time (in seconds) that otters spent extracting meat from the artificial foraging tasks and natural prey types was affected by challenge type (‘T’ denotes ‘task’ on the x-axis labels). Black boxes denote fitted extraction times from otters in the Newquay group, and the grey boxes represent fitted extraction times from otters in the Tamar group. The bold line within each box indicates the 50th percentile and the top and bottom of each box signify the 75th and 25th percentiles, respectively. The whiskers signify the highest and lowest values that are not outliers. Outliers are represented by the points above the boxes. For a plot of the raw extraction times, please see electronic supplementary material, figure S2.