Animals who live in the wild face many sources of harm. Conflicts between animals are one of these that cause great misery to animals. These conflicts between species can take the form of predation or parasitism. Conflicts are also common within species over territory, food, mating opportunities, and through sexual coercion. These conflicts can lead to severe acute injuries, some of which may become chronic, as well as causing fear and stress. Many animals are also killed through these conflicts.
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In a previous section, we saw one form of conflict between animals that is very common: parasitism. In this chapter, we will see some of the other conflicts that can commonly occur between animals and that can result in serious harms. We’ll first see the ones that take place among animals of the same species. Afterwards, we’ll look at harms due to conflicts with animals of other species.
Animals of the same species fight to secure food, territory, mates, or social status within a group. Some animals eat members of their own species. Fighting can result in injury or death. We’ll look at some of these harms.
Territoriality is a widespread cause of intraspecific conflict. It occurs when an individual animal defends a particular area (the territory) against intrusion by other animals, and there by maintains exclusive access to food, nesting sites, or mates. Animals use a variety of methods to demarcate and defend their territories, from scents to sounds to ritual displays. Sometimes, however, animals use force to defend their territories, and this means risking injury or even death for the defender or the intruder.1
Many species of birds are territorial, at least during the breeding season, and some will fight to defend their territory.2 These fights can be brutal, leaving one or both parties with painful injuries. Blackbirds are extremely territorial, with both males and females fighting to protect their territory.
Intergroup violence is common among chimps. Such conflicts usually center around control of territory or the kidnapping of fertile females. Also, big cats are frequently territorial. Tigers are generally solitary, maintaining individual territories. Generally, fights over territory result in the weaker individual submitting, though sometimes injury or death can result.3
Many ant species are highly territorial. Honey ants have specialized workers called repletes. The repletes are fed by the other workers and are used as living larders, storing honey for the winter. When one colony is significantly stronger than another, it will raid the weaker colony, killing or driving away the queen, enslaving the workers and capturing the honey-rich repletes to feed their own colony.4 In order to access the honey, the workers chew through the abdomen of the repletes.
Polygyny is a mating system in which a single male lives and mates exclusively with multiple females. This system has been observed in elephant seals, gorillas, pheasants, and baboons. Since the numbers of males and females inmost species are approximately equal, polygynous mating systems lead to competition between males for access to females. Elephant seal males fight to control a beach and thereby to have exclusive mating rights over the females in that territory. A successful male can have a harem of up to 100 females, while most males will not have a chance to mate at all. The fights between males can be brutal, especially when the males are evenly matched.
Having offspring is generally a much bigger investment of resources for females than it is for males –it is females who undergo pregnancy or lay eggs, who provide most of the parental care, and, in mammals, who provide milk for their young. Male investment of energy and resources is much lower. Males therefore tend to adopt a reproductive strategy that focuses on maximizing their number of mates, while females tend to adopt a strategy of having fewer, higher quality mates. Males coerce females into mating with them, by physically forcing them to mate, harassing them until they accede, or by punishing refusals to mate.
Sexual coercion is common among animals of many species, including insects, fishes, birds, bottle-nosed dolphins, and primates. The victim usually struggles and attempts to escape and is often immobilized by the attacker. In some cases, it results in severe injury from actions like scalping (tearing the skin over the head) in water birds. The rape attempts can be made individually or in groups, like the “rape flights” performed by groups of drakes. The risk of injury is high and the severity of the act may lead to the drowning of the assaulted animal.5
In social animals,social status is important because a higher rank may mean better access to mates and resources like food and territory. Chimpanzees have been witnessed killing members of their own groups over social status, mating rights, or in apparent political power struggles. Sometimes the loser in a power struggle is chased away, and sometimes attacked or killed.
Cannibalism is common in nature. In many cases, cannibalism is practiced on infants. In some cases, this allows the cannibal to eliminate the progeny of a rival. In other cases, it is the parent who kills, and sometimes consumes, their own children. This behavior has been observed in different species of aquatic animals, birds, rats, sloths, and beetles. It isn’t always clear what causes parents to kill their own children. In some cases, it maybe to cut their losses or recoup the energy expended in a “bad investment,” for example, if the infants are developing too slowly, are sick, or there isn’t enough food for them all. The parent might be starving or stressed, due to difficult environmental conditions. In some cases, parents kill their offspring in order to make themselves available for mating so they can “try again” for a better brood.
Whenever an animal has multiple offspring at once, there is the potential for sibling rivalry. Food and parental attention are limited. In situations where the resources available aren’t sufficient, either because of poor environmental conditions or the large size of the brood, siblings have to compete with each other for the resources they require.
Siblicide is frequently observed in birds. Nazca boobies are large seabirds whose chicks almost always engage in siblicide. The mother lays one or two eggs in each clutch. The first chick is usually born around five days before the second, and almost invariably kills the younger sibling by dragging him from the nest.6
Spotted hyena cubs are born with their eyes open and with developed teeth, and they begin fighting each other shortly after birth.7 These fights function to establish rank, but in times of intense food competition, they can result in death. The strongest cubs may not kill the weakest directly, but they can limit their access to their mother’s milk, eventually starving them to death.
Animals may be killed by animals of other species in a variety of ways. The time it takes for the victim to die also varies. For instance, sometimes animals are eaten alive. Some small animals are killed by the digestive enzymes of those who eat them. Some spiders paralyze animals with venom before injecting them with digestive enzymes which liquify the animal’s body. Depending on the kind of venom and the size and species of the captured animal, they may still be alive and capable of feeling pain during this process. Some others are eaten while still alive instead of being killed first. Among them, some are swallowed and digested alive, while others are disemboweled. The vast majority of animals are invertebrates, and most conflicts are fought among them.
Animals who avoid being captured also suffer in a variety of ways from the presence of threatening animals. When they share an environment with such animals, they may suffer from psychological distress, as well as poor nutrition because they are too afraid to graze in dangerous open areas. For its part, hunting is a dangerous activity too. It is common for predatory animals to be injured or killed while hunting. They can suffer accidents by losing their footing in high speed chases over difficult terrain or be injured during the struggle with the animal they are hunting. If the injury is severe enough to prevent them from hunting, they may die of starvation.
1 Harrington, F. H. & Mech, L. D. (1979) “Wolf howling and its rolein territory maintenance”, Behaviour, 68, pp. 207-249; Begon, M.; Townsend, C. R. & Harper, J. L. (2006) Ecology: From individuals to ecosystems, Oxford: Blackwell, pp. 132-133.
3 Mazák, V. (1981) “Panthera tigris”, Mammalian Species,152, pp. 1-8.
4 Hölldobler, B. (1976) “Tournaments and slavery in a desert ant”, Science, 192, pp. 912-914; Hölldobler, B. (1981) “Foraging and spatiotemporal territories in the honey ant Myrmecocystus mimicus wheeler (Hymenoptera: Formicidae)”, Behavioral Ecology and Sociobiology, 9, pp. 301-314.
5 McKinney, F. & Evarts, S. (1998) “Sexual coercion in waterfowl and other birds”, Ornithological Monographs, 49, pp. 163-195; Connor, R. & Vollmer, N. (2009) “Sexual coercion in dolphin consortships: A comparison with chimpanzees”, in Muller, M. N. & Wrangham, R. W. (eds.) Sexual coercion in primates and humans: An evolutionary perspective on male aggression against females, Cambridge: Harvard University Press, pp. 218-243; Garner, S. R.; Bortoluzzi, R. N.; Heath, D. D. & Neff, B. D. (2010) “Sexual conflictinhibits female mate choice for major histocompatibility complex dissimilarity in Chinook salmon”, Proceedings of the Royal Society B: Biological Sciences, 277, pp. 885-894; Han, C. S. & Jablonski, P. G. (2010) “Male water striders attract predators to intimidate females into copulation”, Nature Communications, 1, a. 52.
6 Anderson, D. J. (1990) “Evolution of obligate siblicide in boobies: A test of the insurance egg hypothesis”, The American Naturalist, 135, pp. 334-350.
7 Frank, L. G.; Glickman, S. E. & Light, P. (1991) “Fatal sibling aggression, precocial development, and androgens in neonatal spotted hyenas”, Science, 252, pp. 702-704