Use of space in two neighboring groups of the howler monkey Alouatta palliata mexicana (Primates: Atelidae): overlap and home range size

Abstract

The interaction between primate groups and the dynamics involved in the use of space are important factors affecting both competition for resources and intergroup dominance. In the present study we analyzed the differences in home range overlap and intergroup size, as well as the diversity of tree species within the home range, the Value Index for the key tree species, and the daily activity pattern of two neighboring groups of the howler monkey Alouatta palliata. From March 2002 to June 2003, the behavior and location of two groups of monkeys (G1, two adult males, four adult females and four infants; G2, six adult males, five adult females, one juvenile and three infants) were recorded in the same forest patch at Los Tuxtlas Biosphere Reserve, Veracruz, Mexico. Using the Minimum Convex Polygon (100 %), grid (100 m), and Kernel (adapted and fixed) methods, as well as transect sampling, significant differences (F 1, 20 = 14.45, P = 0.001) were found in the home range size of the groups, being greater in G2. The habitat in the G2 home range had greater richness and diversity of tree species, as well as a higher Importance Value Index for the key tree species (Ficus spp.) included in the howler monkey diet. On the other hand, significant differences between groups (Mann-Whitney U = 38, P < 0.05) were found only as regards locomotion behavior, likely due to a behavioral adaptation to optimize food resource use or search. The two groups displayed a similar use of food resources; however, there was a slight overlap in the home range between both groups with no direct aggression, likely because their habitat included sufficient space and food. Our data suggest that the reduced overlap may vary between neighboring groups because of factors such as group size. However, groups could weigh various factors to avoid home-range overlap.La interacción entre grupos vecinos de primates y la dinámica en el uso del espacio son factores importantes durante la competencia por los recursos y la dominancia intergrupal. En este trabajo analizamos las diferencias intergrupales con relación al tamaño y traslape del ámbito hogareño así como la diversidad de especies arbóreas, el Índice de Valor de Importancia de especies clave y el patrón diario de actividad de dos grupos vecinos de monos aulladores Alouatta palliata mexicana. De marzo 2002 a junio 2003 registramos la conducta y las ubicaciones de dos grupos de monos (formados, G1 por 2 machos adultos, 4 hembras adultas y 4 infantes, y G2 por 6 machos adultos, 5 hembras adultas, 1 joven y 3 infantes) en un mismo fragmento en la Reserva de la Biósfera Los Tuxtlas, Los Tuxtlas, Veracruz, México. Aplicando los métodos de Polígono Mínimo Convexo (100 %), Rejillas (100 m), y Kernel (adaptado y fijo) así como un muestreo por transectos se encontraron diferencias significativas (F 1, 20 = 14.45, P = 0.001) en el ámbito hogareño de los grupos, siendo mayor el de G2. El hábitat en el ámbito hogareño del G2 tuvo una mayor riqueza y diversidad de especies arbóreas así como un valor más elevado en el...