Year: 2024
Type: dissertation
Abstract: Eusociality is the most extreme form of social organization and is defined by three main characteristics: (1) reproductive division of labour, (2) overlapping generations within a group or colony, and (3) cooperative brood care amongst colony mates. Being a unique phenomenon, the evolution of eusociality has been under study for a considerable amount of time. Why an individual would forgo reproduction for the benefit of another has perplexed many behavioural ecologists. In known mammals, eusociality is found in just two species of rodents. The more extreme of the two is the naked mole-rat, which resides in expansive colonies with potentially hundreds of individuals, but only one dominant female and 1-3 males reproduce. The vast majority of their offspring are socially subordinate and remain in the colony and tend to colonial needs, such as colony defense, tunnel burrowing, foraging, and pup care. Some offspring, however, disperse from the colony to begin afresh. How do these offspring, or subordinate individuals, decide on their colonial role? What influences these subordinates to remain in the colony, take on specific roles or temperaments in the colony, or leave it entirely? In this thesis, I explore the social development of the subordinate naked mole-rat and attempt to elucidate the specific characteristics that define the behavioural phenotypes they fall into as adults, and how these phenotypes may have developed from early life experience. After outlining the longitudinal project that makes up the data chapters, I first dive into whether subordinate naked mole-rats can be divided into discrete phenotypes, and if circulating steroid hormone levels underpin these behavioural phenotypes. Next, I test the hypothesis that the partner preference test can be used to interrogate social decision-making in this species, revealing individual differences in behaviour that are consistent with discrete social phenotypes. Furthermore, I build a social network to gain insight into intra-colonial relationships in naked mole-rats, and hypothesize that reproductive caste, behavioural phenotype, and litter order will influence colony member interactions, as well as colony network patterns. Finally, I explore the effects of early life experience on adult social phenotype, and I hypothesize that care given by different colony members (mother versus father versus siblings) will influence behavioural phenotype in adulthood. The emerging data from all four data chapters support the notion of distinct phenotypic characteristics, albeit with considerable variation. Ultimately, this thesis helps to understand the behavioural development of the naked mole-rat, specifically in the subordinate caste, and contributes to the study of evolution of mammalian eusociality and its distinction from other eusocial taxa.
Source: TSpace (University of Toronto)
Author: Toor, Ilapreet
Language: English
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7133001929