Studies on the biology and ecology of the warthog 'Phacochoerus Aethiopicus Sundevalli' Lonnberg, 1908 in Zululand

Abstract

Warthog biology, population structure and behavioural ecology were studied over a two-year period in the Hluhluwe-Corridor-Umfolozi Game Reserve complex, Natal. Age-speci fie stages of tooth replacement, eruption and attrition were described and incremental layers in the cementum were evaluated as correlates of age. Criteria for distinguishing between three age classes of warthogs in the field were described. Carcass yield, physical condition, postnatal and allometric growth were investigated and body mass measurements were compared with data for other warthog pupulations. Parameters of male sexual function were correlated with age and a seasonal fluctuation was found. Breeding was seasonal with a peak in conceptions during May and peak farrowing in November early in the wet season. Mean prenatal litter size was 3, 21 foetuses per female and the prenatal sex ratio was not significantly different from unity. A minimum farrowing rate of 95,S % was recorded during the study period. Lactation endured for about five months and the post partum re conception interval was slightly longer. Habitats with short grass areas were preferred and the availability of holes was not a population limiting factor. The highest local seasonal density exceeded 35 warthogs per kmi and the population age structure was characterised by a large base of juveniles. Recruitment into the yearling age class was substantial. The disparate 0ex ratio of it :2,18~~ among adults was found to generally agree with ratios from other warthog populations, but had probably been exag9erated by male-biased culling. Grasses constituted the bulk of warthog food throughout the year but there was a dry season change in emphasis towards more grass rhizomes, which were dug up with the rhinarium. Holes were very important in warthog_welfare although adult warthogs. particularly were not absolutely dependent on holes for their survival. Thermoregulatory behaviour was a conspicuous feature of warthog activities •. Mean group size was 3,28 and social structure was based on four main types of sounders: solitary adult males, bachelor sounders, heterosexual sounders of yearlings and matriarchal sounders. Warthogs were sedentary· and lived in small overlapping home ranges but territorial defence was absent. Agonistic displays between mature males appeared to be related to dominance mostly in respect of mating priority. Scent marking behaviour was observed and other forms of communication were outlined. Some generalisations were made regarding the adaptive significance of the tusks and warts and the mode of fighting. Courtship behaviour was described and observations of mating season activities showed that warthogs are polygamous. The sows of matriarchal sounders were generally solitary when about to farrow and the piglets were born underground. Piglets started emerging from the hole and grazing before the age of one month, but were almost two months old when they started accompanying their mothers throughout the day. Yearling progeny may rejoin their mothers after the latter have farrowed. A combination of the warthog removal programme and an increasing lion population appeared to have inhibited the rate of increase of the warthog population. Findings are related to suggested management of the warthog population.