Chemosensory discrimination of identity and familiarity in koalas
Charlton, BD 2015, Behavioural Processes, vol. 119, no. 1, pp. 38-43.
Male koalas can differentiate between the scent gland secretions of familiar and unfamiliar individuals. The koalas spent more time sniffing scents from unknown males than familiar males, demonstrating that they can discriminate between members of their species with regards to their familiarity. These results suggest koalas use chemical cues to figure out the identity and familiarity of other koalas.
By presenting different sternal gland scent samples from male koalas housed in separate areas to the testing individuals, and hence unfamiliar to them, the change in sniffing duration showed that the koalas could discriminate between different individuals’ scents. Researchers presented the koalas with four scent samples from the same koala and a different individual’s scent as the second to last. There was an increase in sniffing events between the third sample of the same individual and the different individual’s sample, and a decrease in sniffing events and duration between the different individual and the final sample of the initial individual, demonstrating that the koalas knew it was a different individual. The results were also tested against communal and solitary housing and combinations of scent donors to ensure the response was solely due to the individual’s identity. The number of sniffing events and time spent sniffing was increased when the koalas were presented with unknown samples compared to samples from familiar males, supporting the hypothesis that male koalas can discriminate scents based on familiarity.
Previous studies have shown that male koalas use their sternal glands to mark trees, especially in unfamiliar environments, likely to establish territories and aid in finding mates. While this study is the first to show that the male koalas can identify individuals based on the secretions, it is not clear whether they would be able to recognise those different individuals. Other studies of various mammals have found increased sniffing responses to unfamiliar individuals, which are more likely to interact aggressively, suggesting that male koalas may increase their sniffing response to find and determine the competitive ability of any rivals. Male koalas often share ranges, especially during the breeding season, meaning that familiarising themselves with scents of nearby individuals can allow cohabitation through reducing direct physical contact and competition.
Through understanding the ability of koalas to differentiate between various familiar and unfamiliar individuals, we can reach a greater comprehension of behaviour, habitat and movement. This result is especially significant during the breeding season, as it would dictate male koala behaviour relating to approaching potential mates and rivals.
Summarised by Laura Wait
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