Reproductive biology

Golden jackals (C. aureus) are common on the scrubby sand dunes just south of Tel Aviv in Israel. In December a young adult female approaches an adult male who, by his marking behavior, has established a territory for himself. The female is playful and submissive. The male is not very responsive at first and snaps at the female but she follows him and over the next two months they are seen resting and grooming together until they are seldom seen apart. Sometimes the female stands directly in front of the male to form a "T" and the male may put his forepaws on her back. In March the female is fully sexually receptive for about a week and some of the male's mountings end in a copulatory tie in which the head of his penis swells so it cannot be extracted for 4-5 minutes. Nine weeks later a litter of five pups is born in an underground den. For the first few days after giving birth, the female stays with and nurses the young while the male provides her with food. Soon after their eyes open at two weeks the pups start to crawl around and usually emerge above ground at about three weeks. The parents usually take turns staying by the den and foraging. Most food is carried back in the parents' belly and regurgitated, but larger items may be carried back whole. By three months the pups have achieved nearly adult size and over the next three months they become independent of their parents (although willing to beg if the opportunity presents itself).

Snowy Woods And Wolves

A gray wolf (Canis lupus) pack at the edge of a snowy woods in California, USA. Gray wolves are not found in the wild in California, but may be found in fenced-in parks or other areas. (Photo by Tom Brake-field. Bruce Coleman, Inc. Reproduced by permission.)

The reproductive biology of the jackals in Israel is typical for the majority of the canids. The two salient features are monogamy and regurgitation, a combination that is common in birds but not seen in any other group of mammals. The two are linked. By having an efficient way to provision his young, a male canid can usually be more successful repro-ductively by helping his offspring than by attempting to mate with many females. Monogamous bonds, in all species studied to date, extend over several breeding seasons and are sometimes life-long. (In the pack-living species, most mating occurs between the alpha animals in the male and female hierarchies. Although a pair bond develops, it is determined by the outcome of competition within the sexes.)

Canids are almost always territorial. It pays a pair to keep other members of their species out of a defined area. This protects food supplies, keeps conspecifics away from the den where cannibalism could occur and perhaps most importantly keeps members of the opposite sex away from mates. It is striking that in territorial encounters aggression is usually between members of the same sex. Territoriality is not seen in African wild dogs that roam over such large ranges that they cannot defend its boundaries. However, one pack will chase another away if they meet. At the other end of the spectrum, the home ranges of bat-eared foxes overlap considerably. They live almost exclusively on insects. Food taken by other foxes does not reduce a resident's supplies and defense is not economic in this situation.

A territory that can supply the needs of a breeding pair can often provide food for other animals to survive. In many circumstances it is very beneficial for a young animal to remain on the territory where it was born. Most of the mortality in canids happens when young animals first move away from their natal range. Their hunting skills are not perfect, and they have to move though land occupied by hostile conspecifics (and not infrequently human persecutors). The retention of young in the parental territory is now known to be very common in the dog family. These animals may stay through one or more breeding seasons. These extended families usually gather for a morning and evening greeting although each individual will find food alone. Young from previous years are often present at the birth of the next litter, and regurgitate food and act as babysitters. In most cases this appears to help the parents reproductive efforts, but in one case the "helpers" in a pack of African wild dogs under food stress were seen to pull food from the mouth of the young pups. It is probable that pack hunting developed when pre-existing groups cooperated to tackle larger prey. Even the wolf, when it is living in forested or more arid regions, breeds in pairs and lives in the summer on comparatively small prey. Packs and group hunting occur in the winter.

The rule of monogamy has a few exceptions. In African wild dogs, the alpha female has been seen to mate with more than one male during her estrus, and the hierarchy among the males is unstable so that in different years the same reproductive female will mate with different males. The species is effectively polyandrous, a system in which one female has

Silverback Jackal
A silverback jackal (Canis mesomelas) mother nursing her cubs. (Photo by K & K Ammann. Bruce Coleman, Inc. Reproduced by permission.)

many male partners (despite the fact that at any one moment there is close relationship between the alpha pair). African wild dog females also produce very large litters averaging 10 pups. There is intense competition in this species between females to monopolize the help (in the form mainly of males) needed to raise their pups. At the other end of the spectrum there are cases in several fox species and most notably in the bat-eared fox of two females sharing a den with a single male. This is a form of polygyny in which a male has several female partners and it is also observed in red foxes. In contrast to the African wild dogs in which the regurgitation and hunting skills of the pack are crucial for survival of the pups, in the largely insectivorous bat-eared fox, the male can contribute little to his mate. An insect diet does not provide the nutritious surplus that can be regurgitated. In this species the male's main investment is to babysit while the females forage and produce milk. It is the same effort to babysit one versus two litters, and the females should choose to breed in the areas of most reliable insect abundance. Females usually produce one litter a year and in temperate regions birth usually comes in early spring. Pups require the most food several weeks after they are born, and an early spring birth peak means that growing young can be provisioned from the prey born in early summer. Litter size runs from two to 20 with an average of 5-6. Litter size is larger than that of the other carnivore families. The maned wolf, a large, solitary species with a largely vegetarian diet, gives birth usually to just two young while African wild dogs and Arctic foxes may give birth to 15-20 young. In the Arctic foxes the large litters occur in years of maximum lemming abundance.

Pregnancy And Childbirth

Pregnancy And Childbirth

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