Bringing home the biggest bacon: a cross-site analysis of the structure of hunter-kill profiles in Neotropical forests
Introduction
Subsistence hunting has been a critical form of protein acquisition for tropical forest dwellers since the earliest Stone Age hunters (Stanford and Bunn, 2001). This is particularly the case for many indigenous, mestizo and colonist communities that remain physically isolated, and have little or no access to other sources of animal protein.
Anthropologists were the first to systematically describe the issue of subsistence hunting by indigenous communities, and record settlement-based information on social and cultural factors that may affect different hunting practices and their outcomes in terms of game vertebrates consumed. In these studies, a settlement sample of hunter-kill records (hereafter, harvest profiles) were often a by-product of a more general investigation on traditional patterns of forest resource use, particularly in relation to diet.
Although the levels of indigenous protein intake often appear to be more than sufficient, the strategies used to maintain them can be extremely variable, reflecting a wide variety of cultural and ethnographic contexts involved in this subsistence activity (Balée, 1985, Beckerman, 1994). Game harvest profiles could thus be affected by feeding taboos against some target species, locally enforced bag limits on numbers of individuals killed, spatial or seasonal restrictions to hunting areas or certain species, limits on the age and sex of individuals of a prey population, and hunting technology in terms of traps and weapons used to capture different target species. However, the distinction between what could be described as culturally selected precautionary practices that may prevent future game shortages and mere adaptive responses to a history of local game depletion remains unclear.
Local extinction events in prey species assemblages is a non-random process governed by morphological, metabolic, and reproductive traits, which are usually correlated with body mass (Peters, 1983). Large body size is one of the most frequently cited traits facilitating extinction events, probably because it is associated with low reproductive rates, low population densities, long generation time and long lifespans (Hennemann, 1983, McKinney, 1997). Large game mammals may thus share a set of common life history traits that make them particularly vulnerable to overhunting. The structure of harvest profiles could thus be primarily affected by the availability of large-bodied mammals, which are often preferred game species (Peres, 1990, Alvard, 1993, Bodmer et al., 1994).
In this paper, we attempt to explain differences in the composition and relative abundance of mammal species consumed by neotropical rural folks, using a comprehensive compilation of hunting studies quantifying terrestrial vertebrate kills brought into tribal and nontribal settlements. We provide evidence that a gradual shift from large to small-bodied prey species is widespread and that cultural factors, such as feeding taboos, seem to play a minor role in determining the overall composition of target species. To that end, we relate key parameters summarising game harvest profiles to information on the age and population size of human settlements to examine how the history and scale of hunting could affect the residual mammal assemblage in a given catchment area. Finally, we discuss how prey selection by neotropical subsistence hunters could be affected by ecological rather than socio-cultural constraints.
Section snippets
Compilation criteria
Data on neotropical hunting kill records were compiled from the literature, initially on the basis of the seminal review by Redford and Robinson (1987). In addition to all studies incorporated in their analysis, an extensive search of more recently published and unpublished studies was carried out. The following selection criteria were used in compiling these studies: (1) tropical forest was the predominant vegetation type within the hunting catchment area; (2) hunting was conducted exclusively
Results
Settlements examined here were on average 193 strong (S.D.=169.9, range=25–690 inhabitants, n=31) and had been established from 2 to 25 years (mean ±S.D.=15.9±9.2 years, n=27) prior to each study. The total length of these studies varied from 28 to 877 days (237.7±187.5 days), and they recorded an average number of 259±383 mammal kills (range=30–1780) belonging to as few as seven and as many as 24 mammal species (mean=14.5±5.4 species).
The seven colonist settlements considered here did not
Discussion
A number of studies have shown that tropical forest hunters have a narrow range of preferred species that will be targeted whenever possible, regardless of their local abundance and extinction probability (Hawkes et al., 1982, Vickers, 1991, Bodmer, 1995, Fa and Peres, 2001). As predicted by optimal foraging theory, this preference is consistently skewed towards larger species yielding the greatest amount of meat per unit of energy or time allocated. For instance, the cost of shotgun cartridges
Conclusions
We have provided evidence that changes in the structure of mammal assemblages due to game hunting, as seen from the perspective of kill-profiles obtained by subsistence hunters, is a widespread phenomenon in Neotropical forests. This is consistent with estimates of the residual game abundance at forest sites subjected to varying degrees of hunting pressure, where overhunting often results in vertebrate biomass collapses, mainly through declines and local extinctions of large-bodied mammals (
Acknowledgments
We thank the authors of all hunting studies compiled here. Two of the unpublished harvest studies included in this analysis were funded by a grant from the Center for Applied Biodiversity Science of Conservation International to CAP. We thank Renata Pardini, Anina Carkeek and the participants of the 3rd Course of Quantitative Ecology and Conservation Biology at the Instituto de Pesquisas Ecológicas (IPÊ) for valuable comments on this manuscript. Financial support for AJ was provided by a
References (61)
- et al.
Managing wildlife to conserve amazonian forestspopulation biology and economic considerations of game hunting
Biological Conservation
(1994) Effects of hunting on western Amazonian primate communities
Biological Conservation
(1990)- et al.
Body mass in comparative primatology
Journal of Human Evolution
(1997) - et al.
Shotguns, blowguns, and spears: the analysis of technological efficiency
Testing the “ecologically noble savage” hypothesisinterspecific prey choice by piro hunters of Amazonian Peru
Human Ecology
(1993)Shotguns and sustainable hunting in the neotropics
Oryx
(1995)- et al.
The Sustainability of subsistence hunting in the neotropics
Conservation Biology
(1997) - et al.
Aspectos da caça no alto rio Aripuanã
Acta Amazonica
(1979) - Balée, W., 1984. The Persistence of Ka'apor Culture. PhD Thesis, Columbia University, New...
Ka'apor ritual hunting
Human Ecology
(1985)