Epsilon Archive for Student Projects

Abstract

The naked mole-rat is one of few truly eusocial mammals that we know of today. They live in large colonies consisting of 25 to approximately 295 individuals that are separated in different work casters, mostly depending on age, size and reproductive activity. Almost every colony has a single dominant breeding female, the queen. The rest of the colony is reproductively supressed through behavioural interactions with the queen. When she dies, the females in the colony fight for the vacant position. The social hierarchy that exist within a colony of naked mole-rats depends on a variety of factors, one of the most important being behaviour and behavioural interactions.
A colony of naked mole-rats has, since the middle of 2015, been kept at Skansen-Akvariet in Stockholm. Before arriving the colony lost its queen and according to the staff at Skansen-Akvariet, there has still not been any observation of a new successor. The aim of this study was to observe and analyse the colony and see if it was possible to see a hierarchy within the group. This was done by observing different behaviours and by weighing all the animals. Previous studies shows that it is possible to use a variety of different behaviours to calculate a ranking between individuals in a colony of naked molerats. Because of this, a second aim of this study was to analyse the applicability of these behaviours and, if possible, see which is the most accurate in deciding the hierarchy in a colony of naked mole-rats. Seven different behaviours were selected for this study – mating, shoving, passing over, carrying material, digging, carrying food and agonistic behaviours. The colony at Skansen-Akvariet was observed during ten days using a behavioural-scanning method for the registration of all behaviours.
Mating was the only behaviour that was not observed at any time during the study and it was only Nr. 10 that performed shoving. The three individuals, Nr. 5, Nr. 8 and Nr.10, which were the biggest and oldest females in the colony, performed a high frequency of dominance-linked behaviour throughout the study period. This result indicates that these three are at the top of the hierarchy and most likely to become the new queen of the colony at Skansen-Akvariet. Because of the correlation between the different behaviours, weight and age, this study shows that all of the selected behaviours is applicable for determining social hierarchy in a colony of naked mole-rats. It is however recommended to use more than one behaviour for a more reliable result.