WALLACE RESOURCE LIBRARY Module 03 – Animal Behaviour D01 – Bull elephant dominance relationships after contraception.

Introduction to the Pongola African Elephants High densities of elephants in fenced reserves can lead to negative impacts on the vegetation. Elephant population control is necessary as part of any effective conservation management programme. Male contraception has been argued as the most effective form of control for discrete populations of elephants. 2 forms of contraception are possible and practical: Testosterone hormone suppression drugs that can be injected by darting. Vasectomy of young bulls Hormones suppression (testosterone) is less invasive but can cause serious problems with herd dynamics. Background to the research: As high densities of elephants in fenced reserves can lead to permanent, negative impact on vegetation, elephant population control is a necessary part of game reserve management. Contraception has been argued to be the most effective control method for discrete elephant populations. Due to their smaller numbers in comparison to females, contraception of bull elephants is the most cost effective method of contraception. There are two possible methods of bull elephant contraception: hormone suppression and vasectomy. Hormone suppression is a less invasive method (elephants just need to be darted with hormones rather than undergo surgery), but can cause serious problems with herd dynamics due to reduced levels of testosterone in the bulls. Sexual activity in mature male African elephants is predominantly associated with the occurrence of musth. Musth is a condition which refers to a set of physiological and behavioural characteristics including heightened aggression and an elevation in testosterone secretions. Although bulls show signs of sexually activity from around 12-15 years old, bull elephants are not fully mature until they reach 40 years of age. Thus, the older the bulls, the more musth they experience and this heightened testosterone and aggression determines their position in the dominance hierarchy. The hormone secretions of older bulls also suppress musth in younger bulls, which is very important for controlling younger bull behaviour. In the absence of older bulls, younger bulls can display heightened rates of aggression and abnormal behaviour. Interfering with the hormones of bull elephants is therefore best avoided, which is why vasectomy is the preferred method of bull elephant contraception because vasectomy prevents conception, but does not affect male hormones. Dominance among bull elephants is generally associated with body size and age, which in turn is linked to musth. The outcome of social interactions between bulls can also be used to determine their position in the hierarchy. These interactions include: aggression, submissive displays, placing the trunk over the back of another individual, and interlocking tusk behaviour (see Figure 1). Each of these interactions will have a winner and a loser and the number of wins and losses by each bull can be used to determine their position in the hierarchy. However, in order to do this, you must be able to identify each individual elephant in the population so you know exactly who is interacting with whom. Although vasectomies are a successful tool for elephant population control and the physiological effects of vasectomy are well understood, little is known about the influence of vasectomies on behaviour and the overall dynamics of a herd. In theory, male behaviour should be unaffected by vasectomies because hormonal levels remain unchanged. However, it is possible that rates of male sexual behaviour or female interest in vasectomised males will change after sustained periods of unsuccessful mating, which may have a knock on effect on male dominance interactions. This current study aimed to investigate dominance interactions of bull elephants at Pongola Game Reserve following the vasectomies of seven of the eight adult bulls to determine whether dominance was related to age or had been affected by the vasectomies.

Introduction to the Pongola African Elephants This study involved the vasectomy of the bulls in a small herd (8 bulls and 57 other individuals). In 2008, 7 young bulls were vasectomized but the old bull (Ingani) did not undergo the operation as the risks were too great for such a large animal. Vasectomies prevent the bull being fertile but do not affect the testosterone levels and hence the behaviour of the animal. These are some of the key questions that will be answered in this lecture, although there will be many more. At the end of the lecture, see if you can answer these questions, and if you can’t then see if you can find out more to help you.

Behaviour study to determine the Dominanace ranking amongst the 8 bulls Data was collected by recording dominance interactions (aggression, trunk over back, tusk interlocking and submissive displays) between pairs (dyads) of bull elephants. This data was used to plot a matrix which could then be used to determine a dominance rank order for the bulls. Each bull can be identified by using an ID chart.

Research Questions How do you identify individual elephants based on their physical appearance? Is the dominance hierarchy of bull elephants at Pongola determined by age or has it been affected by vasectomies? Research question: 1. How do you identify individual elephants based on their physical appearance? 2. Is the dominance hierarchy of bull elephants at Pongola determined by age or has it been affected by the vasectomies? IF YOU OPEN THE FILES “M03 D01 DOMINANCE COMPLETED” and “M03 D01 AGE AND DOMINANCE COMPLETED” YOU CAN SEE THE FULLY ANALYSED DATASETS. Answer and discussion to the research question: 1. Bull A = Ingani, Bull B = Khumbula, Bull C = Lucky, Bull D = Ntini, Bull E = Asiphephe, Bull F = Mgangane, Bull G = Kohlewe, Bull H = Shayisha 2. Our data indicates that the dominance hierarchy of bull elephants at Pongola is determined by age. This means that the hormones and behaviour of the bull elephants have not been adversely affected by the vasectomies. You will notice that the scatter plot does not show a nice diagonal line, but this is to be expected, considering that many of the bulls are of the same age (and therefore similar body size). However, Ingani is the oldest bull and is clearly the most dominant. Similarly, Shaisha is the next oldest and clearly dominant to all other bulls apart from Ingani. The rest of the hierarchy does follow the age of the bulls, but as Asiphehpe, Khumbula, and Ntini are all the same age, their dominance ranks are most likely determined by slight differences in body size or personality.

Discussion? The bulls can easily be identified using ID charts. The data suggests that the dominance hierarchy seems to be determined by age. The hormones and behaviour of the bulls have not been adversely affected by the vasectomies. The scatter plot is not as clear as expected and possibly due to many of the bulls being of similar age. The differences seen between the bulls of the same age are most likely determined by slight differences in body size and personality.