Demography of a Collared Peccary Population in South Texas

• Published in: The Journal of wildlife management 1995-01, Vol.59 (1), p.153-163
• Main Authors: Hellgren, Eric C., Synatzske, David R., Oldenburg, Perry W., Guthery, Fred S.
• Format: Article
• Language: English
• Subjects: Age; Age structure; Animal and plant ecology; Animal populations; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Demecology; Demography; Fetus; Fundamental and applied biological sciences. Psychology; Herds; Mammalia; Mammals; Mortality; Peccaries; Population characteristics; Reproduction; Sex ratio; Survival rates; Tayassu tajacu; Vertebrata
• ISSN: 0022-541X; 1937-2817
• DOI: 10.2307/3809128

Population dynamics of large herbivores in semiarid environments are regulated by rainfall. Reductions in reproduction and juvenile survival are the main mechanisms of regulation. We examined population characteristics of a harvested collared peccary (Tayassu tajacu) population in South Texas to model population responses to harvest. We sampled a peccary population from 1974 to 1993, intensively collecting data from 1989 through 1993. Mean (±SE) ovulation rate (2.13 ± 0.03, n = 181) and litter size (1.89 ± 0.03, n = 151) of adults did not vary by age class (P = 0.15) or year (P = 0.94), although litter sizes of yearlings (10-21 months old) (1.71 ± 0.19, n = 7) tended (P = 0.07) to be smaller than age-class 3 adults (5-7 yr old). Minimum age at predicted primiparity was 20 months. Pregnancy rate was positively associated (χ = 6.20, P = 0.013) with rainfall in the previous year. Estimated fecundity (F young/F/yr) for yearlings and adults was 0.41 and 1.0, respectively. The sex ratio of harvested animals (53.3% M, n = 1,125, P = 0.027) was skewed toward males. Lack of age-specific variation (P = 0.23) in postnatal ratios suggested that harvest was not sex specific. Age structure varied (P = 0.08) among years, with fewer old animals in 1989-93 harvests. Male and female annual survival estimates were 0.90 ± 0.17 and 0.87 ± 0.05, respectively, from 1977 to 1983 telemetry data for unharvested herds, and did not differ (P = 0.88). From life table analyses of harvested herds from 1989 to 1993, male and female annual survival estimates were 0.65 ± 0.03 and 0.73 ± 0.04, respectively, and did not differ (P = 0.13). Year, age, and reproductive status affected (P < 0.05) condition indices, namely kidney fat, total mass, and eviscerated mass. Population modeling provided an estimated rate of juvenile (≤9 months) survival of 0.32 to maintain a stationary population under the 1993 harvest rate of 20%. We propose that juvenile survival is compensatory to adult mortality attributable to hunting. Relationships among juvenile survival, density, and forage resources need field investigation to explore the effect of density-dependent survival on dynamics of peccary populations.