Sustainability of Harvest of Culpeo Foxes in Patagonia
Total Page:16
File Type:pdf, Size:1020Kb
ORYX VOL 29 NO 1 JANUARY 1995 Sustainability of harvest of culpeo foxes in Patagonia Andres J. Novaro Wildlife hunting, for meat and skins, is an important component of the rural economy in Argentinian Patagonia. Every year thousands of fur-bearing mammals are killed and the impact of this on their populations is unknown. This paper reports on the results of a preliminary investigation into the sustainability of the harvest of culpeo foxes Dusicyon culpaeus in a 1000-sq-km area of Neuquen Province. Monitoring of fox densities and harvest rates over 5 years on six ranches revealed that, despite intense hunting, the numbers of foxes remained little changed. On the other hand, life-table analysis suggested that the levels of hunting pressure on four ranches were too high to allow fox populations to persist unless they were boosted by immigration. The findings have applications for wildlife managers in establishing sustainable harvest rates and optimal spatial distribution of those rates. Hunting for fur-bearing mammals is wide- has not been well studied and government spread throughout Argentinian Patagonia. agencies and the general public consider Every winter thousands of culpeo foxes sheep and cattle ranching to be the only signif- Dusicyon culpaeus and Patagonian grey foxes icant economic activities in the region. D. griseus, hog-nosed skunks Conepatus chinga Between 1975 and 1985, an average of and C. humboldtii, and Geoffroy's and Pampas 460,000 skins of 'grey' fox (a description that cats, Felis geoffroyi and F. colocolo, are captured includes the Patagonian grey fox and the with leg-hold traps, shot or hunted with dogs. Pampas fox D. gymnocercus) were exported Culpeo fox hunting, in particular, is di- from Argentina (Garcia Fernandez, 1991). rected towards reducing sheep predation These exports reached a peak in 1979, when (Bellati and von Thungen, 1990) and is also an over 1.2 million skins of those two species important source of income for rural people. were exported. Exports have declined since On sheep farms in southern Neuquen 1979. The export of culpeo fox skins followed Province, north-west Patagonia, many ranch a similar trend, but with smaller numbers workers each hunt between 10 and 25 foxes a (Figure 1). It is not clear if these declines in year (Novaro and Funes, unpubl. data). For legal exports were the result of decreasing these people, with salaries of $US120-300 a population sizes, increasing domestic use of month, and culpeo fox skins worth an average fox furs (which is significant in the case of the of $US15 each, culpeo fox hunting alone repre- culpeo), or increases in illegal exports (Garcia sents 4-26 per cent of their annual income. In Fernandez, 1991; Novaro, 1993). addition, these people also hunt introduced On a regional scale, the numbers of foxes European hares Lepus capensis for cash, and hunted are equally impressive and variable guanacos Lama guanicoe, rheas Pterocnemia pen- from year to year, although data available are nata, armadillos Chaetophractus villosus and much more limited. In southern Rio Negro Zaedyus pichiy, and introduced red deer Cervus Province, northern Patagonia, 791-21,000 elaphus for meat. Thus, wildlife hunting is an foxes (grey and culpeo) were hunted during important component of rural economies in the six years from 1988 to 1993 (Figure 2) Patagonia, although its relative importance (Subsecretaria de Fauna, 1988, 1989, 1990, 18 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.19, on 03 Oct 2021 at 22:02:39, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300020822 SUSTAINABILITY OF HARVEST OF CULPEO FOXES IN PATAGONIA 10 r 25 20 i5 6- 10 I988 I989 I990 I99I I992 I993 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 Figure 2. Harvest of Patagonian grey fox Dusicyon culpaeus and culpeo fox D. culpaeus in Rio Negro Figure 1. Exports of culpeo foxes Dusicyon culpaeus province between 1988 and 1993 (from Subsecretaria from Argentina between 1976 and 1990) from Garcia de Fauna, 1988,1989,1990,1991, and M. Alcalde, Fernandez, 1991). pers. comm.) • , culpeo fox; H, Patagonian grey fox 1991, and M. Alcalde, pers. comm.). (Caughley, 1977) and ran simulations with the The impact of this harvest on populations of computer programme RAMAS/age (Anon., fur-bearers as well as on all other species 1990; Novaro, 1991). The trend in culpeo hunted is unknown. In 1989 I initiated a study abundance was simulated in 30 replicates run of population trends and the impact of hunt- for 50 years. ing on culpeo and grey foxes in southern Between 1989 and 1993 I monitored culpeo Neuquen Province (40°S and 71 °W). The pur- and grey fox densities using the scent-station pose of this paper is to report the results of a method (Roughton and Sweeny, 1982) on six preliminary evaluation of the sustainability of ranches (Catan Lil, Los Remolinos, La Papay, the harvest of culpeo foxes in this intensively Cerro de los Pinos, Collun-Co and La hunted area. Rinconada) with a total area of approximately 1000 sq km. Most hunting occurred on the first four ranches and there was little or no hunting Methods on the latter two. I estimated harvest rates and some population parameters through the col- An analysis of the dynamics of a harvested lection of fox carcasses from local hunters population of culpeo foxes was conducted (mainly ranch workers). Preliminary estimates using data on age structure and fecundity of culpeo densities were obtained by combin- from Crespo and De Carlo (1963). These ing scent-station with capture data (Novaro, authors worked in the same study area 30 1991) and from live captures and an on-going years earlier, collecting carcasses from local radio-telemetry study (Novaro et ah, 1993). hunters. I considered that it was appropriate These estimates of fox density were compared to use their data because hunting methods, with harvest rates to evaluate the proportion human populations and land-use systems had of the population removed annually. not changed in the area in the last 30 years. Thus, it was expected that the human impact on fox populations had changed little. Reanalysing their data, I built a life table ORYX VOL 29 NO 1 JANUARY 1995 19 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.19, on 03 Oct 2021 at 22:02:39, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300020822 A. J. NOVARO 160 20 250 200 120 150 80 40 1989 1990 1991 1992 1993 -•- culpeo density, g culpeo hunted Figure 4. Population trend of culpeo foxes (in proportion of scent stations visited) and minimum number of foxes hunted in the study area in southern Neuquen between 1989 and 1993 (from 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 3032 Novaro and Funes, unpublished data). Years Figure 3. Simulation of culpeo abundance over time Furthermore the sex ratio in the culpeo with population characteristics derived from Crespo population has changed during the last 30 and De Carlo (1963). years in the direction expected from the re- sponse to increased hunting pressure. Crespo Results and discussion and De Carlo (1963) estimated a sex ratio sig- nificantly biased towards males (0.69 females The estimated age structure of the harvested to 1 male, n = 254), whereas the preliminary culpeo population in 1963 was 105, 55, 6 and 1 data from the same area for the present study foxes in 0, 1, 2 and 3-year-old age classes, re- showed that the sex ratio now is not signifi- spectively. The fecundity rate was 1.06 cantly different from a 1:1 ratio (0.92 females (pups/adult-year), and the survival rates for to 1 male, n = 102; Novaro, 1991). A change in age classes 0,1 and 2 were 0.52, 0.12 and 0.17, sex ratio from one biased towards males to a respectively. The preliminary simulation balanced one or biased towards females has based on these data showed that culpeo popu- been observed in other canids subject to in- lations could not maintain their numbers and tense hunting pressures, for example coyote eventually would collapse under the harvest Canis latrans (Knowlton, 1972; Berg and levels at the time (Figure 3). Chesness, 1978), and is interpreted as a mech- Because culpeo foxes are still abundant in anism that allows populations to withstand the area, I wondered if harvest rates could high mortality rates temporarily. have declined during the last three decades The population trend of culpeos in the area since the population age structure data were shows that in spite of intense hunting their collected. This was probably not the case, be- numbers remain little changed and have in- cause fur prices increased during the mid- creased slightly (Figure 4). I was not always 1970s (Ojeda and Mares, 1982), producing a able to determine the total number of foxes higher demand for fox furs, and remained hunted because of logistical problems, so only high in the region until the late 1980s (Novaro the most reliable figures were considered. The more than twice and Funes, unpubl. data). minimum number of foxes known to have 20 ORYX VOL 29 NO 1 JANUARY 1995 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.19, on 03 Oct 2021 at 22:02:39, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms.