Mating system of the Eurasian badger,Meles meles, in a high density population

Abstract

Badgers are facultatively social, forming large groups at high density. Group-living appears to have high reproductive costs for females, and may lead to increased levels of inbreeding. The extent of female competition for reproduction has been estimated from field data, but knowledge of male reproductive success and the extent of extra-group paternity remains limited. Combining field data with genetic data (16 microsatellite loci), we studied the mating system of 10 badger social groups across 14 years in a high-density population. From 923 badgers, including 425 cubs, we were able to assign maternity to 307 cubs, with both parents assigned to 199 cubs (47%) with 80% confidence, and 14% with 95% confidence. Age had a significant effect on the probability of reproduction, seemingly as a result of a deficit of individuals aged two years and greater than eight years attaining parentage. We estimate that approximately 30% of the female population successfully reproduced in any given year, with a similar proportion of the male population gaining paternity across the same area. While it was known there was a cost to female reproduction in high density populations, it appears that males suffer similar, but not greater, costs. Roughly half of assigned paternity was attributed to extra-group males, the majority of which were from neighbouring social groups. Few successful matings occurred between individuals born in the same social group (22%). The high rate of extra-group mating, previously unquantified, may help reduce inbreeding, potentially making philopatry a less costly strategy.

Using genetic methods to investigate dispersal in two badger (Meles meles) populations with different ecological characteristics

“…Territorial behaviour in Woodchester Park was very pronounced, with nonoverlapping group ranges and intensive territorial markings (Cheeseman et al, 1981). The average territory size in this locality has been reported as 0.26 km 2 (Cheeseman et al, 1981) and the average distance between main setts as 0.57 km (Carpenter et al, 2005).…”

“…A large number of loci deviated from HardyWeinberg genotypic proportions in the UK population. However, the 16 loci used in the present study were developed from individuals captured in Woodchester Park (Carpenter et al, 2003), in which no systematic heterozygote deficiencies were observed when performing analyses on adults and cubs separately (Carpenter et al, 2005). The deviations from Hardy-Weinberg proportions are therefore not an intrinsic characteristic of these loci (see also Frantz et al, 2004;Pope et al, 2006), but very likely the result of the strong spatial autocorrelation pattern observed in the UK study area (Frantz et al, 2009).…”

“…According to Carpenter et al (2005), approximately 30% of both males and females reproduced each year in the high-density Woodchester Park population contained within our UK study area. Taking the effective population size to be (Hartl, 1988), the effective density should equate roughly to 0.6 Â census density.…”

“…British badgers were genotyped at 16 badger microsatellite loci (Carpenter et al, 2003) as described previously (Carpenter et al, 2005), but excluding locus Mel116 (because of inconsistencies in scoring). In the Swiss samples (which were genotyped at a later date), all 16 loci were amplified in two multiplex PCR, using the Qiagen multiplex Kit (Qiagen, Hilden, Germany).…”

Molecular marker‐based pedigrees for animal conservation biologists

“…They note that a large proportion of the paternities are inferred to be from unsampled males from outside of the study area and conclude that promiscuity is a strategy to minimize inbreeding. Carpenter et al (2005) also made use of a molecular marker-based pedigree in their recent study of the Eurasian badger Meles meles mating system. They also found that badgers exhibit high levels of extra-group matings, attributed to inbreeding avoidance, and suggest that the tactic could help social cohesion by reducing the cost of philopatry.…”