Promiscuous mating in feral pigs (Sus scrofa) from Texas, USA

Abstract

Context Feral pigs represent a significant threat to agriculture and ecosystems and are disease reservoirs for pathogens affecting humans, livestock and other wildlife. Information on the behavioural ecology of feral pigs might increase the efficiency and effectiveness of management strategies. Aims We assessed the frequency of promiscuous mating in relation to oestrous synchrony in feral pigs from southern Texas, USA, an agroecosystem with a widespread and well established population of feral pigs. An association between multiple paternity of single litters and synchrony of oestrous may indicate alternative mating strategies, such as mate-guarding. Methods We collected gravid sows at nine sites in southern Texas during 2005–07. We used a panel of DNA microsatellite markers to estimate frequency of multiple paternity and the distribution of male mating among litters of feral pigs. Conception dates were determined by fitting average fetal crown–rump measurements within litters to expected fetal development relative to gestation time. Key results We found evidence of multiple paternity in 21 of 64 litters (33%) from seven of nine sites sampled. Synchrony of oestrous did not influence promiscuous mating, as we found multiple paternity at sites with synchronous and asynchronous oestrous. Males sired from 8 to 11 offspring at three sites where >10 litters were sampled. Mean litter size (5.4) was less than the best-fit value for the number of offspring, indicating that some males sired offspring with ≥ 2 females. Key conclusions Feral pigs in Texas appear to be promiscuous under a range of demographic conditions, unlike wild boar and feral pigs in other regions. The ecological and behavioural factors affecting multiple paternity are not clear, but may include male–male competition, harassment avoidance, genetic benefits for offspring, response to macro-habitat conditions, or selection. Implications A high incidence of sexual contact among individuals may increase the opportunity for diseases transmitted by oral or venereal routes, such as swine brucellosis and pseudorabies. In addition, fertility-control methods targeting males only are likely to be inefficient if female promiscuity is high; methods targeting females or both sexes jointly may be more effective.

On the evolutionary consequences of increasing litter size with multiple paternity in wild boar (Sus scrofa scrofa)

“…The mating system of this species has been originally described as polygynous (Mauget 1980;Dardaillon 1984), which is consistent with the sexual dimorphism displayed by the species (Ralls 1977). Interestingly, with the rise of molecular genetic techniques, a growing literature has shown that multiple paternity occurs (Delgado et al 2008;Poteaux et al 2009) and may be common in some populations of wild pigs (Delgado-Acevedo et al 2010;Costa et al 2012). A positive effect of multiple paternity on litter size has even been highlighted in the domestic pig (Sus scrofa domesticus), which is the domestic counterpart of the wild boar.…”

Reproductive characteristics of wild boar males (Sus scrofa) under different environmental conditions

“…Young males leave their family packs when they are approximately one year old and form their own packs outside of the family groups. The mating system is commonly described as polygynous (Fernández-Llario et al 1999), some authors, however, describe it as polygynandrous or promiscuous (Pérez-González et al 2014) in view of evidence of multiple paternity within litters (Delgado-Acevedo et al 2011).…”

Heterozygosity decrease in wild boar mating system ‐ a case of outbreeding avoidance?

“…The outbreeding avoidance based on different parental genomes might produce problems of genetic diversity conservation and, hence might reduce the fitness of individuals (e. g. Acevedo‐Whitehouse et al ., ). This trend might be counteracted with other processes that favour the genetic diversity maintenance such as seasonal partner switch, litter production, multiple paternity, sex‐biased dispersal and mate competition (Karl, ; Delgado‐Acevedo et al ., ; Pérez‐González et al ., ).…”