Ecology of the bushpig Potamochoerus porcus Linn. 1758 in the Cape Province, South Africa

Seydack, Armin H. W. (Stellenbosch : Stellenbosch University, 1990-12)

Thesis (PhD) -- Stellenbosch University, 1990.

Thesis

ENGLISH ABSTRACT:Bushpig sociology, energetics, reproduction and population dynamics were studied over an 8-year period in the Cape Province, South Africa. The social organization was found to be strikingly different from that known from other suid species. The basic social unit is a unimaternal family group, occupying a resource-based territority, with a monogamous mating system. This form of social organisation is related to the dispersed nature of food resources, to which it provides exclusive access. It is reminiscent of canid social systems. Agonistic behaviour, communication and maternal behaviour were studied as the opportunity arose. The average home range size was 7,2 kmª, ranging from 3,8 to 10.1 kmª. Home ranges were often traversed within 1-4 days, as part of territory patrolling. The average diel ranging distance was 3 km. Bushpig were active during both night and day and exhibited a basic bimodal rhythm. The main phase of intensive foraging occurred from before dusk to midnight, with a secondary activity peak after dawn. Activity schedules were geared to avoid extreme ambient temperatures. Temperature regulation and water use were investigated, with particular reference to thermoregulatory behaviour (nest building). pelage characteristics, body core temperature dynamics, thermoneutral zones and resting metabolic rates. The thermoneutral zone for 10 kg bushpig juveniles was estimated to lie between 13° and 30°C and that for adults between 8° and 25°C. Foraging behaviour, diet and its nutritient content were investigated. Regional differences in the nutritional quality of bushpig diets in the Eastern and Southern Cape were associated with the predominance of nutrient-rich and nutrient-poor substrates respectively. These in turn were reflected by divergent life history features in the populations from the two regions. Patterns of growth and energy storage were described and the value of various parameters (e.g. mass to size ratio, fat depositions, blood composition) to evaluate condition was investigated. In studying reproductive biology, sexual maturation, female reproductive cycles, prenatal litter statistics, foetal development, 1actation, breeding seasonality and reproductive turnover were the main aspects addressed. The role of food quality, body condition and social status in determining reproductive success was discussed. Bushpig population density estimates in the Southern Cape ranged between 0,3 and 0,5 animals/kmª• The dynamics of Southern and Eastern Cape populations were found to differ. The differences are consistent with the hypothesis that social organisation is determined by the distribution and availability of food while diet quality shapes life history tactics. A life history model was developed which links edaphoclimatic environmental conditions with diet quality, metabolic turnover rate and, ultimately, life history features. In the concluding chapter some of the managerial implications of the research findings are discussed.

AFRIKAANSE OPSOMMING:Die sosiologie, fasette van die energiebalans (temperatuurregulasie, voeding). voortplanting en bevolkingsdinamika van bosvarke is in die Kaapprovinsie (Suid-Afrika) oor 'n tydperk van 8 jaar bestudeer. Dit kon bewys word dat die sosiale organisasie van die bosvark van die van ander varksoorte verskil. Die basiese sosiale eenheid bestaan uit 'n familiegroep wat slegs 'n enkele telende moederdier bevat. Ruimtelike organisasie is gebaseer op 'n stelstel van voedingsterritoriums. 'n Monogamiese paringstelsel kom voor. Die yl verspreiding van voedsel word as die onderliggende rede vir die sosiale organisasie beskou. Gedragspatrone (kommunikasie, aggressie, grootmaak van kleintjies) is bestudeer soos die geleentheid voorgekom het. Heelwat ooreenkomste is gevind tussen die sosiale organisasie van die bosvark en lede van die hondefamilie. Die gemiddelde woongebiedgrootte is 7,2 kmª (tussen 3,8 en 10,1 kmª). Woongebiede word gewoonlik binne 1-4 dae deurkruis en dus soos territoria gepatroleer. Die gemiddelde daaglike bewegingsafstand was 3 km. Bosvarke was beide gedurende die nag en die dag aktief en het 'n bimodale aktiwiteitsritme gevolg. Die hoofaktiwiteitsfase van intensiewe voeding het tussen sononder en middernag plaasgevind, met 'n sekondere fase na sonop. Soedoende is temperatuuruiterstes vermy. Temperatuurregulasie en watergebruikpatrone is bestudeer, insluitend temperatuurreguleringsgedrag, haarkleedeienskappe, liggaamskerntemperature, termoneutraliteit en metabolise omset. Voedingsgedrag, voedsel en die voedingswaarde daarvan is ondersoek. Verskille tussen die Oos- en Suid-Kaap in die kwaliteit van voedsel hang saam met die laer vlak van voedingsstowwe in die gronde van die Suid-Kaap. Bosvarkbevolkings in die twee streke toon verskille in populasiedinamika wat hieraan toegeskryf kan word. Groei- en energiestoorpatrone is beskryf. Die moontlikhede is ondersoek om kondisie te evalueer met behulp van parameters soos massa tot grootte-verhoudings, vetneerleggings en bloedwaardes. Aspekte van voortplantingsbiologie, soos geslagsrypheid, vroulike voortplantingssiklusse, voorgeboortelike werpselgroottes, foetale ontwikkeling, laktasie, seisoenaliteit en voortplantingsomset is behandel. Die rol van voedselkwaliteit, kondisie en sosiale status by die bepaling van voortplantingsukses word bespreek. Skattings van die bevolkingsdigtheid van bosvarke in die Suid-Kaap het gewissel tussen 0,3 en 0,5 diere per kmª• Op grond van die verskille in bevolkingsdinamika tussen bosvarke in die Suid- en Oos-Kaap is 'n model ontwikkel om die verband tussen bevolkingsregulering en lewensstrategieeë (life history tactics) te verklaar. Hiervolgens het voedselbeskikbaarheid die tipe sosiale organisasie bepaal terwyl die lewensstrategieë van bevolkings die gevolg is van voedselkwaliteit. Die model stel vaar 'n verband tussen groeipleksomstandighede, voedselkwaliteit, metaboliese omset en bevolkingsdinamika. In die laaste hoofstuk word sommige van die bestuursimplikasies van die navorsingsbevindinge bespreek.

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