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A H Harcourt

Publications and source records attributed to A H Harcourt.

7 recordsLinked to original sources
PubMed2001

Primate evolution: a biology of holocene extinction and survival on the southeast Asian Sunda Shelf islands.

What biological traits distinguish taxa susceptible to extinction from less susceptible taxa? Substantiated island biogeographic theory suggests that after insularization, small islands lose more species than do large islands. Thus, susceptible taxa are those now found on only large islands. The traits of susceptible taxa can thus be found by comparing the biology of species found only on large islands with those also found on small islands. The islands examined here are those of the Sunda Shelf, created as a result of the Holocene rise in sea levels of 120 m. We use four statistical comparisons: comparative analysis by (phylogenetically) independent contrasts (N = 8 contrasts at the subgeneric or deeper level), Spearman correlations, stepwise regression, and principle components analysis (N = 9 subgenera/genera). The genera and one subgenus considered are: Hylobates, Macaca, Nasalis, Nycticebus, Pongo, Presbytis, Symphalangus, Tarsius, and Trachypithecus. Traits of risk appear to be large body mass, low density, large annual home range, and low maximum latitude. Expected traits that did not correlate with susceptibility were low interbirth interval, high percent frugivory, high group mass, low altitudinal range, and small geographic range. The risky traits also apply to just the anthropoids (i.e., prosimians excluded). The risky traits are explained if susceptibility is induced by requirements for a large extent of habitat, a small population size, and specialization. These findings, which indicate that efficiency and plasticity of use of the environment separate susceptible from successful primate taxa, might be relevant to an understanding of hominoid evolution.

Altitude↗
PubMed1994

Sexual selection and genital anatomy of male primates.

Correlations between mating system and various aspects of genital anatomy suggest a strong influence of sexual selection on genital morphology. We test the generality of the influence by examining whether primate taxa in which there might be enhanced sexual selection (those with multi-male mating systems) possess, as expected, relatively more spinous penises than do taxa with other mating systems. As most prosimians, but few anthropoids (monkeys and apes), possess penile spines, and because the predominant mating systems of the two taxa differ, taxonomic constraints are taken into account. Sexual selection apparently does not act on penile spines in the same manner as on other aspects of genital anatomy: spinosity is not greatest in multi-male taxa of either prosimians or anthropoids. In some taxa, spines might stimulate reproductive readiness and synchrony in situations in which the sexes live apart and do not have other means of communicating reproductive state (dispersed social systems and 'stolen' extra-pair copulations), but problems exist with the hypothesis, as they do with the idea that spines are involved with scent marking. It seems that either penile spines have several functions, or penile spinosity in primates, and other orders, remains to be explained.

Animals↗
PubMed1980

Reproduction in wild gorillas and some comparisons with chimpanzees.

Information was collected over a period of almost 12 years on the gorillas of the Virunga Volcanoes region of Rwanda and Zaire, most of it collected since September 1972. Comparisons were made with the Gombe Stream chimpanzee population (values in parentheses). Gorilla females matured at about 8 years (compared with 9-10 years for the chimpanzee) and first bred at 10-11 years (11-12 years). Males started to breed later, possibly at 15 years (about 13 years). Oestrous periods of female gorillas lasted for about 2 days (10 days) and oestrous cycles for about 30 days (36 days). Gestation in the gorilla lasts 255 days (228 days). Intervals between surviving offspring in the Virunga study groups was about 4 1/2 (5 1/2 years) but in the whole Virunga population was nearer 8 years. Lactational amenorrhoea lasted about 2 1/2 years (3 1/2 years). In gorillas and chimpanzees there were about 3 cycles to conception after parturition and females probably produce in their lifetime about 3 offspring that survive to adulthood. A successful male's productivity is greater. Mortality of immature gorillas was about 40% (50%). Initiation of courtship is generally by the female in gorillas but the male in chimpanzees. Copulation in gorillas lasts for about 1 1/2 min (7 sec) and occurs at a rate of once every 3 h when a female is in oestrus (once in 2 h). Interference in copulation is more common in the chimpanzee than the gorilla, but competition between individual males is more intense in gorilla populations. Females of both species can clearly exercise their preferences for particular males. The observed differences between the species in courtship and mating behaviour can be related to differences in the number of males available to and competing for oestrous females: in the loose multi-male chimpanzee community there is more advantage to males in initiating copulation and mating frequently and efficiently, and to females in advertising oestrus, than in the relatively stable one-male mating system of the gorilla.

Animals↗
PubMed1978

Strategies of emigration and transfer by primates, with particular reference to gorillas.

In many primate species, more males than females leave their natal group and transfer to another. In man, chimpanzee and the gorilla, however, the reverse is the case. This paper presents detailed data for the gorilla on individuals' movements into and out of breeding units. Comparisons are made with other primates, and with data on two non-primate species in which females rather than males move between breeding units. Proximate causes and functions of emigration and transfer are considered, and the reasons (proximate and evolutionary) for the observed sex differences in frequency of movement are discussed.

Age Factors↗