And now, for my favorite animal in the world:
The Eurasian Badger. (
Meles Meles)
Eurasian Badgers live in social groups of, on average, 6 adults (although groups as large as 23 have been recorded). Sociality was not recognized in this species until fairly recently, however, since badgers are only seen by humans when the animals are out alone at night to forage. More detailed study has revealed that they actually live together in large underground catacombs called "setts." These are systems of interlocking tunnels with nest chambers, toilets, and several entrances. Badgers inherit setts from their parents generation after generation, while always expanding and refining them. The result is huge tunnel systems that are, in some cases, actually centuries old. Excavation of a sett in England revealed that it contained 879 meters of tunnels, 50 chambers, and 178 entrances. The researchers estimated that its construction required the removal of 70 tons of soil! Genetic analysis has shown that members of badger social groups or "clans" are closely related. Through radiotracking it has been determined that this is due to delayed dispersal, resulting in family groups remaining together. Females are even less likely than their brothers to leave the sett in which they were born. Clans often consist of a dominant male, a dominant female, and their subordinate offspring. The dominant pair are generally the only individuals that successfully produce cubs, although all or most of the females mate with the dominant male. Subordinate females often become pregnant, but on the few occasions when the pregnancy is carried to term the dominant female generally finds and kills the resultant cubs. Subordinate badgers do not seem to be "helpers at the nest," as are found in some birds and a few mammals. Although it is difficult to observe badgers since they are only above ground at night, it seems clear that subordinates do not bring food to the nest for the breeding female or her cubs. They do, however, participate in sett excavation and the airing of nest material, but not at significantly higher rates after the birth of a litter. (Nest material is frequently carried to a sett entrance where it is aired in the sunshine for several hours, probably cutting down on external parasites.)
Badger clans are territorial, defending an area (50 to 150 hectares) that contains their home sett and several foraging areas. They delineate their territories by placing latrines, areas where all clan members urinate and deficate, at regular intervals along the borders. Territories are also outlined by the paths that the badgers use when patrolling the boundaries. They mark both paths and latrines with the copious and decidedly odoriferous secretions of their subcaudal glands. Badgers, especially males, will aggressively defend their territories against intruding foreign badgers.
The functions and patterns of sociality in this species are not well understood. It is possible that climate is an important factor. Average group size varies throughout their range, and in some areas, such as southern Europe, they seem to be solitary. Where badgers live singly or in pairs the climate tends to be warm, and their setts are small and simple. In colder areas the setts are dug down below the depth to which the ground freezes, and the whole clan sleeps together in one nest chamber, possibly for warmth. Thus large, cooperative groups may be necessary for the construction of deep setts and the sharing of body heat, although this hypothesis has not been thoroughly tested.
Badgers remain fairly common in much of their range, probably because they are able to live among humans. It is not uncommon in England for the range of a group of badgers to include suburban developments, especially since some people intentionally leave food out for them. A matter of some concern is the preservation of historic badger setts. Since some of these constructions are centuries old, citizens have sometimes successfully argued for their preservation despite proposed real estate and infrastructure developments.