Begging in animals is when an animal solicits being given resources by another animal. This is usually a young animal soliciting food from their parents, brood hosts or other adults. However, the resource is sometimes non-food related or may be solicited by adult animals. Begging behavior is most widely studied in birds, however, mammals, amphibians, and invertebrates perform begging displays. Generally in food solicitation, begging behavior is instinctive, although in some instances it is learned (e.g. pet cats and dogs).
While the ultimate causation for begging is an increase in the animal's individual fitness, several theories have been proposed for how food begging evolved proximate causes including scramble competition, honest signalling of need, and cooperative begging by siblings. Various types of information such as nutritional status or immunocompetence can be transmitted with auditory and visual begging signals and the behavior can be modulated by several factors such as brood size and hormones. Similarly, several costs of begging have been investigated including energetic, growth and predation cost. Begging from humans also occurs under artificial circumstances such as donkeys, elephants and dolphins begging for food from tourists.
History In 1950, Tinbergen and Perdeck tested the effects of visual stimuli on begging behavior of gull chicks, elucidating which characteristics of their parents' bills the chicks were reacting to.Tinbergen, N. and Perdeck, A.C., (1950). On the stimulus situation releasing the begging response in the newly hatched herring gull chick (Larus argentatus argentatus Pont). Behaviour, 3: 1–39Alcock, J., (2009). Animal Behavior, Ninth Edition. Sunderland, MA: Sinauer Associates. Using models varying in different characteristics, they tested multiple stimuli and found that gull chicks pecked most at a long, red bill with contrasting white bars at the end. Chicks also pecked at other models; in decreasing order of begging intensity were a two-dimensional cardboard cut-out of the head of a gull with a red spot on its bill, simply a bill with a red spot, and a cut-out of a gull's head with no red spot on the bill. These studies showed the chicks were responding to the red spot stimulus on their parents' bills, an example of imprinting.
In 1953, Von Haartman first demonstrated that chick begging is a stimulus to parental feeding and that the begging level of the brood increases with deprivation.von Haartman, L.V., (1953). Was reizt den Trauerfliegenschnapper (Muscicapa hypoleuca) zu futtern? Vogelwarte, 16: 157–164 (cited by Cotton et al. (1996)
Strategies Parent–offspring conflict describes the evolutionary conflict arising from differences in optimal fitness of parents and their offspring. While parents tend to maximize the number of offspring, the offspring can increase their fitness by getting a greater share of parental investment often by competing with their siblings. Food distribution by parents among offspring is a key element in the parent-offspring conflict. Young animals are potential competitors and attempt to skew parental food allocation in their favor; this is most often attempted by conspicuous begging displays. Several models have been proposed to explain the evolution of conspicuous offspring solicitation. One model predicts that begging intensity is driven by scramble or sibling competition.Harper, A.B., (1986). The evolution of begging sibling competition and parent-offspring conflict. American Naturalist, 128: 99–114 A second model is that begging intensity reflects the true condition or need of the individual and that the cost of the signal imposes honesty.Godfray, H.C.J., (1991). Signalling of need by offspring to their parents. Nature, 352: 328–330 A third model predicts that animals respond to the overall signal of the entire brood and that the siblings cooperate to gain the most food.Mathevon, N. and Charrier, I., (2004). Parent-offspring conflict and the coordination of siblings in gulls. Proc. Biol. Sci., 271: S145–S147.
Sibling competition
Begging behavior possibly functions in sibling competition. This is the method by which individuals seek to gain more food than their siblings to increase their own individual fitness. Parents need an honest signal from their offspring indicating their level of hunger or need, so that the parents can distribute food accordingly. Offspring want to get as much of the food as possible, so they will want to exaggerate their signals to gain more investment from their parents. However, this conflict is resolved by the cost of excessive begging. Not only does excessive begging attract predators, but it also retards chick growth if begging goes unrewarded.Kilner, R.M. (2001). A growth cost of begging in captive canary chicks. Proceedings of the National Academy of the Sciences, 98(20): 11394–11398 Thus, the cost of increased begging will enforce offspring honesty. A weaker nestling might easily change the intensity at which it begs, but a stronger nestling which is hungry and begging can push to the front of the nest where the parent is.
Competition among nest mates can sometimes encourage adaptations between the siblings. In an experiment where a larger species of bird was placed into a nest with a smaller species, the smaller birds changed the intensity and frequency of their calls to compete with the alien species. The study showed that the smaller birds were fed the same amount as other nestlings in a nest without an intruder.
Honest signalling of need Begging by dependent chicks is known to correlate with hunger level; parents use this as a signal of brood demand to adjust their chick feeding behavior. Studies have been conducted which manipulated the competitive environment of individual European starling (Sturnus vulgaris) chicks by altering the state of nest mates while holding the state of target chicks constant. Begging effort of the unmanipulated target chicks was not affected by the changes in begging behavior of their siblings, supporting the view that in this species, begging is a reliable signal of individual chick state and does not involve responses to the effort of nest mates.Cotton, P.A., Kacelnik, A. and Wright, J., (1996). Chick begging as a signal: are nestlings honest? Behavioral Ecology, 7: 178–182
Cooperative begging The black-headed gull (Larus ridibundus) is a semi-altricial bird with a brood size of one to three siblings. When a parent returns to the nest, its chicks recognize its calls and start begging before the adult lands; begging behaviour is also exhibited when the parent is in the nest. Parents respond to the total solicitation emerging from the nest; therefore, the probability of getting food increases with the number of chicks begging together. The more siblings there are, the more they coordinate their begging while decreasing the number of individual begging bouts. In this way, intra-brood synchronization of begging enables chicks to reduce their effort in begging.
Begging behavior in mongooses is cooperative. Adults are influenced by the total signal emanating from the litter, so that pups who beg at low rates receive more food as litter size increases. Pups increase their begging when litters are reduced or littermates beg at low rates. Bell, M.B.V., (2007). Cooperative begging in banded mongoose pups. Current Biology, 17: 717–721
Non-food solicitation begging African wild dogs (Lycaon pictus) show a ritualised form of begging behaviour which apparently functions as communication of social stability rather than soliciting food. Pack members use body language to show submission to a dominant dog and avoid conflict. They roll over on their bellies or wag their tails. Other signs of submission or appeasement include exposing the throat and food-begging, or licking the corners of the dominant dog's mouth. Pack members show submission towards the alpha female by lying down to “nurse” from her. When two wild dogs meet, they display such submission to one another, muzzle licking, whining, and even regurgitating food to the other. African wild dogs rarely fight over food. If two wild dogs have a piece of food that they both want, rather than inflict injuries upon the other, they will practise "aggressive begging", where they will flatten their ears, curl their lips, lower their front-quarters, curl their tail over their back, and try to crawl under the other wild dog.
Domestic animals, particularly cats and dogs, will often solicit non-food-related resources from humans such as the opportunity for exercise, play, or, grooming. Under these circumstances, the behavior is learned by associative learning rather than instinctive.
Signals given during begging behavior
Begging animals may use one or a combination of signals during begging displays.
Auditory signals Birds use begging calls when they are young in order to obtain attention from their parents to be fed. Begging calls in birds are very important in enabling parents to recognize their offspring. This is important because of the amount of energy expended giving care to and feeding the offspring. Acoustic cues are incredibly important in recognizing chicks. Acoustic cues work over long and short distances, as well as for individual recognition.Levréro F., Durand, L., Vignal, C., Blanc, A. and Mathevon, N., (2009). Begging calls support offspring individual identity and recognition by zebra finch parents. Comptes Rendus – Biologies, 332579-589. 1-11. Birds beg more intensely when they are hungry even though it expends more energy. Larger birds are able to beg longer and expend more calories.Neuenschwander, S., Brinkhof, M., Kolliker, M., and Richner, H. (2003). Brood size, sibling competition, and the cost of begging in great tits (Parus major). Behavioral Ecology, 14: 457–462 Therefore, they are fed more and continue to grow larger.
Nestling tree swallows produce a begging display when their parents arrive at the nest with food, but they also beg to apparently inappropriate stimuli in the absence of parents, such as movements of the nest or broodmates. Begging rate and intensity varied in response to recordings of (1) a tree swallow adult landing on a nestbox and calling and (2) a common grackle (Quiscalis quiscala), a nest predator, landing on a nestbox. Nestlings increased the rate and intensity of their begging responses to both swallow and grackle stimulus sounds as time without food increased, although responses to the grackle sounds were always less than to the swallow sounds.Leonard, M.L., Horn, A.G. and Mukhida, A., (2005). False alarms and begging in nestling birds. Animal Behaviour, 69: 701–708
When cuckoo chicks were reared in the nests of four hosts (reed warbler, great reed warbler, dunnock and meadow pipit), dunnock-cuckoos began begging more rapidly than reed warbler-cuckoos despite growing at the same rate. Perhaps surprisingly, the cuckoos do not vary their begging call note structure to match that of their hosts' chicks.Butchart, S.H.M., Kilner, R.M., Fuisz, T. and Davies, N.B. (2003). Differences in the nestling begging calls of hosts and host-races of the common cuckoo, Cuculus canorus. Animal Behaviour, 65: 345–354
Meerkat pups change their begging behavior by increasing it up to 80 percent more when near adults that give out food at the highest rate versus those that give the least. Pups also beg relatively consistently when next to specific adults, indicating there is an adaptability strategy in the way the pups beg.Madden, J.R., Kunc, H.-.J.P., English, S., Manser, M.B., Clutton-Brock, T.H., (2009). Do meerkat (Suricata suricatta) pups exhibit strategic begging behaviour and so exploit adults that feed at relatively high rates? Behavioral Ecology and Sociobiology, 63: 1259–1268
Visual signals