Estimates of brown brocket deer (Mazama gouazoubira) habitat use at El Bagual Ecological Reserve, Argentina.
RESUMEN. -- Se estim?el uso del habitat por el guazuncho pardo (Mazama gouazoubira) en la Reserva Ecol gica El Bagual, en el nordeste de la Argentina, mediante el conteo de huellas en quatro diferentes comunidades vegetales, en 1988-89. A partir de lecturas repetidas sobre 56 circulos de radio fijo de tres [m.sup.2] de superficie, se calcul?un indice de ocupaci n (nomero de huellas/dias). Las varianzas de los indices en los quatro ambientes muestreados fueron homogeneas y no se registraron diferencias significativas (P>0.05) en el uso mensual de los h[sz]bitats. Vocablo importante: el guazuncho pardo; Mazama gouazoubira; uso del habitat; Argentina.
The brown brocket deer is a poorly known species inhabiting shrubby savannas and forests in South America. They occur east of the Andes and from Venezuela south to northern Argentina (Cabrera and Yepes, 1940). This small deer's social structure is based on family units (Olrog and Lucero, 1981) and it is among the largest herbivorous species in the Chaco Region (Bucher, 1980). The species is important to local economies because it provides meat for aboriginal people and according to Ojeda and Mares (1982), brocket pelts are traded in considerable quantities.
The brown brocket deer is one of three species of cervids, together with the red brocket deer (Mazama americana) and the marsh deer (Odocoileus dichotomus), occurring at El Bagual Ecological Reserve (Yanosky, 1989). Microhabitat preferences appear to separate them (Yanosky, 1989, 1991), the red brocket being found in non-native Eucalyptus forests and the marsh deer in "banados" (flooded grasslands). These species are completely segregated by habitat. Furthermore, the tracks of the three species are easily distinguished with no possibility of track misidentification. No information on seasonal habitat use of brown brockets has been reported. We are the first to have monitored habitat use of this brocket throughout the year at El Bagual Ecological Reserve.
The estimation of wild animal population parameters by sign counts has been widely used, especially for deer (Caughley, 1977; Davis and Winstead, 1980; Telleria, 1986). Ockenfels and Bissonette (1983) developed a track plot system to monitor habitat use and seasonal activity levels in white-tailed deer (Ockenfels and Bissonette, (1982). We applied this same method for the brown brocket deer at El Bagual Ecological Reserve.
MATERIALS AND METHODS
El Bagual Ecological Reserve is a 3,462 hectare protected area located in the Chaco Biogeographical Region of northeastern Argentina (Formosa province). The Chaco is an area comprising grasslands and forests, with equilibrium maintained by floods and fires (Morello and Adamoli, 1974). El Bagual includes banados with sparse woods composed of different plant structure and species. These woods can be classified according to seral stages and have been reported elsewhere (Yanosky and Mercolli, 1993).
The brown brocket deer uses all woody areas at El Bagual: shrubby savannas, early seral stage or forest under formation, low forest and high forest or subtropical jungle (Yanosky and Mercolli, 1989, 1991). These four plant communities are characterized by both herbaceous strata and arboreal elements. The herbaceous stratum is important in the shrubby savannas, but less so in the high forest where the ground is totally dominated by bromeliads that make access difficult. Forest elements are not important features in the shrubby savannas, but are increasingly dominant in the other communities up to high forest, where trees are more than 20 meters high and little sunlight reaches the ground.
Study sites were selected on game trails in each plant community where 14 round plots 3 [m.sup.2] were established in exposed areas. Plots were located on a straight, randomly oriented transect through each habitat type, spaced 100 meters apart and established by disturbing the soil with an axe, then raking the soil and litter up to 10 centimeters deep. Each plot was then swept with a metallic broom so that all tracks would be detected. Track sets indicated that deer passed through the plots in random directions. It was impossible to distinguish separate sets of tracks left by different individuals, so a single hoof impression was considered as one track and all the plots (56) were "read" periodically between December 1988 and November 1989. Efforts were made to read each plot weekly, but heavy rains prohibited this because they frequently erased the track record between sampling visits. We utilized each heavy rain period to initiate a new sampling period. After reading each plot, the plots were swept with the metallic broom leaving the plot prepared for the next sampling.
Data collected from the plots included a count of the total number of deer tracks. An activity index, the number of tracks/day (= NTD), was calculated according to the methodology developed by Ockenfels and Bissonette (1983). NTD indexes were calculated by dividing the total tracks counted in all plots by the number of days in each sampling period and number of plots with or without tracks. We assumed that these values were related to general levels of brocket deer activity, although it is not known if brockets are territorial with discrete home ranges.
Monthly NTD means, seasonal NTD means, and NTD means for each cover type were calculated. Bartlett's test and ANOVA were used for data analysis (Sokal and Rohlf, 1981).
RESULTS AND DISCUSSION
Each sample plot was read 44 times, for a total of 2,464 samples. Each of the habitat types was represented by the same number of readings. A generalized pattern for the period December 1988-November 1989 is shown in Fig. 1.
[FIGURE 1 OMITTED]
Six hundred eighty-nine (28%) of the 2,464 samples contained deer tracks. A total of 5,283 tracks was counted during the period of 984 days: 240 days from the forest under formation, 249 from the shrubby savanna, 249 from the high forest, and 246 from the low forest.
We analyzed the data for differences among habitat use levels. Bartlett's test indicated variances were similar and homogeneous in the four habitat types studied ([X.sup.2.sub.(3)] = 5.23, P>0.1), so ANOVA was used to test for differences among means. NTD means from the four habitat types were not significantly different, that is, the four habitat types did not differ in average use by brocket deer throughout the year [F.sub.(3,44)] = 2.55, P>0.05).
Monthly differences in NTD for forest under formation and shrubby savannas showed the same unimodal behavior with an increase in activity during late summer (Fig. 2). The same parameter is shown in Fig. 3 for high and low forest. Patterns of seasonal occupancy of these two cover types were similar with more homogeneous NTDs throughout the year, but with an increase during late spring. ANOVA was used to test for monthly differences in mean habitat use levels, and nonsignificant differences were recorded for monthly uses ([F.sub.(11,36)] = 1.99, P>0.05).
Seasonal activity levels were obtained for each cover type. Data suggest a proportionately greater use of early successional forest during spring, although ANOVA indicated that habitat use was not significantly different according to seasonal NTDs ([F.sub.(3,12)] = 1.42, P>0.25).
[FIGURE 2 OMITTED]
Although the generalized pattern represented in Fig. 1 shows activity peaks during late summer-early autumn, early and late winter, and late spring, these trends were not statistically significant. Brocket deer appeared to use the four available forest communities to the same extent. These four communities are approximately equally represented in the study area. No preference for any one of these communities was detected in relation to availability.
The brown brocket deer has been extirpated in some regions of its distribution, but its species survival status is somewhat more stable when compared with other species of Mazama because of its wide distribution in South America (Palermo, 1983). Knowledge of population parameters, seasonal activity and habitat use is required to provide management guidelines for this declining species. We hope that the information herein will prove useful for the management of this species in other parts of its range.
We express our appreciation to A. Franzmann for his encouragement and for evaluation of the manuscript. We thank E. Bucher, D. Roby, A. Woolf, T. Lee and J. Dixon for their comments on the manuscript. We are indebted to Alparamis S.A., for financial and logistic support. This is a contribution for El Bagual Ecological Reserve, SC No. 26, Formosa, Argentina.
[FIGURE 3 OMITTED]
Bucher, E. H. 1980. Ecologia de la fauna chaquena. Ecosur, 7:111-159.
Cabrera, A., and J. Yepes. 1940. Mamiferos sudamericanos. Cia. Argentina de Editores, Buenos Aires, 352 pp.
Caughley, G. 1977. Analysis of vertebrate populations. Wiley and Sons. London, 234 pp.
Davis, D. E., and R. L. Winstead. 1980. Estimating the numbers of wildlife populations. Pp. 221-245, in Wildlife Management Techniques Manual (S. D. Schemnitz, ed.), The Wildlife Soc., Washington, D.C.
Morello, J., and J. Adamoli. 1974. Las grandes unidades de vegetacion y ambiente del Chaco argentino. Segunda parte: vegetation y ambiente de la provincia del Chaco. Inta, Serie fitogeografica No. 13. 130 pp.
Ockenfels, R. A., and J. A. Bissonette. 1982. Estimates of white-tailed deer activity levels in Oklahoma. Proc. Ann. Conf. Southeast. Assoc. Fish and Wildl. Agencies, 36:445-453.
______. 1983. A track plot system to monitor habitat use. Proc. Ann. Conf. Southeast. Assoc. Fish and Wildl. Agencies, 37:173-181.
Ojeda, R. A., and M. A. Mares. 1982. Conservation of South American mammals: Argentina as a paradigm. Special Publ. Pymatuning Lab. of Ecol. No. 6:505-539.
Olrog, C. C., and M. M. Lucero. 1981. Guia de los mamiferos Argentinos. Fundacion Miguel Lillo, Tucuman. 151 pp.
Sokal, R. R., and F. H. J. Rohlf. 1981. Biometry. 2nd ed. W. H. Freeman, San Francisco, California. 859 pp.
Telleria, J. L. 1986. Manual para el censo de los vertebrados terrestres. Ed. Raices, Madrid, 278 pp.
Yanosky, A. A. 1989. Fauna Silvestre en la Reserva "El Bagual". Analisis de situacion de la fauna de mamiferos. Actas 1[degrees] Jornadas Nac. Fauna Silvestre (Santa Rosa, Argentina), 1987 (1989): 648-665.
______. 1991. Los mamiferos de la Reserva Privada "El Bagual": abundancia, utilizacion de las comunidades y factores de riesgo. Spheniscus, 9:1-10.
______. 1993. Activity pattern of Procyon cancrivorus (Carnivora: Procyonidae) in Argentina. Rev. Biol. Trop., 41:157-159.
ANGEL ALBERTO YANOSKY AND CLAUDIA MERCOLLI
El Bagual Ecological Reserve, 3601-Pte. Yrigoyen, Formosa, Argentina
|Printer friendly Cite/link Email Feedback|
|Author:||Yanosky, Angel Alberto; Mercolli, Claudia|
|Publication:||The Texas Journal of Science|
|Date:||Feb 1, 1994|
|Previous Article:||Vegetational changes due to prescribed fire in Mission Tejas State Park.|
|Next Article:||Production of pectinases by Exserohilum rostratum.|