Foraging-Based Enrichment Promotes More Varied Behaviour in Captive Australian Fur Seals (Arctocephalus pusillus doriferus)

Abstract

During wild foraging, Australian fur seals (Arctocephalus pusillus doriferus) encounter many different types of prey in a wide range of scenarios, yet in captive environments they are typically provided with a narrower range of opportunities to display their full repertoire of behaviours. This study aimed to quantitatively explore the effect of foraging-based enrichment on the behaviour and activity patterns displayed by two captive Australian fur seals at Melbourne Zoo, Australia. Food was presented as a scatter in open water, in a free-floating ball device, or in a static box device, with each treatment separated by control trials with no enrichment. Both subjects spent more time interacting with the ball and static box devices than the scatter feed. The total time spent pattern swimming was reduced in the enrichment treatments compared to the controls, while the time spent performing random swimming behaviours increased. There was also a significant increase in the total number of bouts of behaviour performed in all three enrichment treatments compared to controls. Each enrichment method also promoted a different suit of foraging behaviours. Hence, rather than choosing one method, the most effective way to increase the diversity of foraging behaviours, while also increasing variation in general activity patterns, is to provide seals with a wide range of foraging scenarios where food is encountered in different ways.

Fig 1. Mobile and Static enrichment devices.

a) Mobile ball and rope enrichment device: fish are placed into the ball, which must then be manipulated by the seal in order to knock out the hidden prey items. b) Static box enrichment device: fish are hidden in the recessed tubes on the front surface of the device. Because the box device is static against the wall it cannot be manipulated to knock out prey items. See S1 Video for footage of the main behaviours used by the seals when interacting with these devices.

Fig 2. Summary of behaviours displayed during feeding trials.

Mean duration (min) of behaviour states performed by Bay (a) and Tarwin (b) during each control and enrichment treatment. Similar behaviour states are grouped to show time spent performing: enrichment-related behaviours, pattern swimming, random swimming or any other behaviour state. Operational definitions for behaviour states are outlined in Table 2.