To communicate with conspecifics is essential for animal reproduction and survival. Olfactory signals are probably the oldest signals used for communication, and have several advantages compared to signals in other sensory modalities, as they work in the dark, around physical obstacles, and in the absence of the sender.
The field of olfactory communication in mammals is still a young field of research and detailed long-term individual-based data are necessary to answer important questions in ecology and evolution. In mammals, olfactory signals are typically complex chemical mixtures rather than single compounds, and are particularly important in carnivores and rodents, where they play an important role in territoriality, reproduction, and recognition of social partners.
Both the European badger (Meles meles) and the Eurasian beaver (Castor fiber) are territorial, nocturnal mammals who rely heavily on olfaction for intra-specific communication. While badgers in the UK can live in groups of up to 30 closely related individuals and have a highly promiscuous mating system, beavers typically live in small family group, and are among the few non-primate mammals that show a typical pattern of social monogamy. In this thesis, we applied a combination of chemical, molecular and behavioural methods to investigate olfactory signals and territorial behaviour in beavers and badgers. We specifically aimed to:
1. Investigate the chemical composition and information content in badger anal gland secretion (AGS), and whether this information is used by badgers (papers I and II)
2. Investigate whether badgers use bacteria in their subcaudal pouch to achieve a shared group-odour (paper III)
3. Investigate the previously assumed monogamous mating system of the Eurasian beaver (paper IV)
4. Investigate how familiarity, threat level and individual properties in olfactory signals affect territorial responses by badgers (paper I) and beavers (papers V and VI)
In papers I and II, we found badger AGS to be highly variable and individual-specific, and that conspecifics could perceive this information. In paper III, we found group differences in badger subcaudal scent composition, but not in bacterial flora. In paper IV, we found evidence of extra-pair paternity in beavers, contradicting previous assumptions of strict genetic monogamy in this species. In papers V and VI, we found beavers to show strict territorial responses to simulated intruders, with especially elevated responses to subdominant conspecifics.
Although badgers and beavers are different species systematically as well as from in their lifestyle, social system, and mating system, there are still many similarities in their communication systems. Both species have complex interactions with their conspecifics, like group members and neighbours, and both have evolved complex secretions for intraspecific communication.
However, this thesis demonstrates that, although both species have been defined as strictly territorial, beavers might be the only one of these two species actually fitting this strict definition