Demographic and Reproductive Parameters of the Yellow-Cheeked Pocket Gopher (Pappogeomys castanops)

-A population of Pappogeomys castanops s imulans was live-trapped on a 3.5-ha study area in Lubbock, Texas, from September 1971 to September 1973. Seasonal and annual differences in population size were observed, with the population fluctuating between 20 and 25 gophers. Female reproductive activity began in January and continued until October, with an obvious period of recruitment lacking; however, a peak was observed in March and April. Females produced as many as three litters per reproductive season. Females born early in the year were sexually mature within the reproductive season of their birth. Females had an average survival rate of 56 weeks in the trappable population as compared to a 31-week survival rate of males. Neonate through subadult survival of pooled males and females was 72.7%. The gophers had a clumped distribution on the study area, with more mature females forming the centers of the clumps. Subadults of both sexes and adult males were distributed peripheral to adult females. Adult females showed few shifts in their home range configuration whereas adult males and subadults of both sexes had more labile home range configurations. Females arranged their home ranges so as to provide isolation from other gophers. Males, on the other hand, tended to align their home ranges so as to contact more animals, especially mature females. Offspring dispersed from the maternal burrows as juveniles or subadults. Colonization frequently occurred adjacent to the maternal home range, although long distance moves also were observed. Once a home range was established, few shifts were observed. Pocket gophers (Family Geomyidae) are among the most variable mammals in cranial, exomorphological, and karyotypic features. This variability has long interested mammalogists, and has been manifested in an abundance of research concerning interand intraspecific variation. An understanding of the overall population biology associated with this variability can provide valuable insight into the general processes involved in evolution. Before the effects of the interactions and dynamics that occur among subspecies and s ~ e c i e s can be understood, however, it is necessary to determine and estimate the demographic parameters that occur within and between populations of the same subspecies. Such studies of geomyid population parameters are primarily restricted to Thomomys (Hansen, 1960, 1962; Howard and Childs, 1959; Ingles, 1952; Miller, M. A., 1946; Miller, R. S., 1964; Vaughan, 1962) and Geomys (Adams, 1966; Wilks, 1963; Wing, 1960; Wood, 1949) with Pappogeomys having received less attention. It is especially important to understand these parameters because Pappogeomys can be found contiguously with Geomys and Thomomys, but it inhabits more xeric areas (Reichman and Baker, 1972) and displays less overall variability in exomorphology and karyology among subspecies and species (Russell, 1969; Beny and Baker, 1972). Studies concerning the population processes are currently limited to assessing movement (Williams and Baker, 1976) and reproductive activity (Ickenberry, 1964). The aim of this study was to assess the demographic and distributional parameters of a population of Pappogeomys castanops. It was hoped that this would provide an insight into the basic population processes of gophers of this genus, and allow comparisons of geomyid life history strategies. A population of Pappogeomys castanops s imulans was trapped from September 1971 to September 1973 on a study site located at the Lubbock Municipal Airport, Lubbock Co., Texas, 988 I . Mamm., 61(2):224-236, 1980 224 May 1980 SMOLEN ET AL.-PAPPOCEOMYS ECOLOGY 225 TABLE 1.-Mean monthly air and soil (45 cm) temperatures and precipitation during the study years (1971-1973). Air temperature and precipitation data were collected by the Department of Commerce, United States Weather Bureau Facility at the Lubbock Municipal Airport. Soil temperature data were collected by the Texas ArLM Experimental Station, 3.2 km north of the study site.