The defense of the cache may be the primary factor favoring solitary living in Dipodomys species (Eisenberg 1963).

Therefore, although these females showed high tolerance for intrasexual overlap, they continued to remain territorial and excluded conspecifics from their core areas. Overall, animals tended to remain in their burrows, with the burrow entrance plugged with soil, until approximately 2230–2300 h. After that, individuals were primarily active in their core areas until early morning. 2002). Because the conventional nearest-neighbor test of Clark and Evans (1954) does not perform well with respect to boundary effects (Meagher and Burdick 1980), we also used a Monte Carlo simulation to examine the spatial distribution of nearest neighbors. 1B). We used incremental analysis to calculate the number of locations necessary to estimate home-range size. Reproductive condition of females was recorded (according to appearance of the vaginal area) as closed and uns wollen (nonestrus), open and swollen (pre-estrus), and fully open and swollen on the edges (estrus—Randall et al. Radiotracking.—Radiotracking was conducted on the 1-ha grid described above. ©2020 Verizon Media. Dynamics of space use and male vigour amoungst wood mice, Ecological and demographic effects on intraspecific variation in the social system of prairie dogs, Reproductive consequences of variation in the composition of howler monkey (. Statistical comparisons of home-range sizes.—Home-range sizes and percent overlap were compared using parametric paired and independent Mests when applicable in SYSTAT 9.0 (Wilkinson 1999). Utilization is important in calculating core areas because it provides a more accurate depiction of the frequency with which an individual uses each point in the habitat (Seaman and Powell 1996; Worton 1989). Kangaroo Rat Removal and Control Large colonies of kangaroo rats can damage rangelands and grasslands by eating large amounts of seed and vegetation.

D. ingens once lived in colonies of thousands of individuals and maintained an extensive geographical range throughout Fresno and Kern counties as well as in San Luis Obispo County (Grinnell 1922). Variation in density, both temporal and spatial, is thought to be primarily a result of interactions between life-history attributes of Dipodomys (adult and neonate weight, gestation time, litter size, and maximum life span) and environmental limiting factors (Brown and Harney 1993).

A.. Travis S. E. Slobodchikoff C. N. Keim P.. Oxford University Press is a department of the University of Oxford. 3. Traps were baited with bird seed. We used Sherman XLK Extra-Large Kangaroo Rat Traps (30.5 × 9.5 × 7.6 cm; H.B. WARNING: You are about to download a 12.5 MB TIFF! We compared home-range size and percent overlap for the 7 females and 4 males monitored in both seasons. We used the minimum convex polygon method because it has been used in other studies on Dipodomys (Braun 1985; Jones 1989; Perri and Randall 1999; Schroder 1979; Shier and Randall 2004; Sullivan 2000), thus allowing comparisons between our results and other data sets. We made it easy for you to exercise your right to vote! Burrow locations were recorded 2–5 h before sunset each day. For the summer season we analyzed 74.2 ± 2.6 (mean ± 1 SE) locations per animal; for the winter season we examined 80.2 ± 0.9 locations per animal. They’re home to these amazing animals doing things beyond what we could ever imagine.”. near kangaroo rat burrows that appeared active. Each territory, or precinct, contains 2–4 burrow openings, a shallow underground system of complex tunnels, and aboveground activity areas such as sand-bathing sites (Grinnell 1932; Randall 2001, 2007). Get all the latest election results from across the country, with up-to-the-minute maps and more. They feed on seeds, green plants, and insects. background Dark Medium Light. All procedures were approved by San Francisco State University Animal Care and Use Committee and conform to guidelines recommended by the American Society of Mammalogists (Animal Care and use Committee 1998). Solitary is not asocial: effects of social contact in kangaroo rats (Heteromyidae: Selection for increased cranial capacity in small mammals during a century of urbanization, Anthropogenic disturbance and chimpanzee (, Activity overlap of carnivores, their potential wild prey, and temporal segregation, with livestock in a Biosphere Reserve in the Chihuahuan Desert, Annual board meeting and awards announcement American Society of Mammalogists, Genetic diversity and conservation of the endemic tuco-tuco, About the American Society of Mammalogists,, Receive exclusive offers and updates from Oxford Academic, Copyright © 2020 American Society of Mammalogists. Thus, males should increase their reproductive success by adopting a spatial strategy that allows them to gain access to multiple females (Bateman 1948; Emlen and Oring 1977). In contrast, home ranges of males increased significantly from an average of 0.02 ± 0.01 ha in the nonbreeding season to an average of 0.09 ± 0.05 ha in the breeding season (Wilcoxon signed-ranks test: Z = 1.825, P = 0.068). In all other species for which comparative data are available, home ranges of males and females are similar in size (Behrends et al. An R-value greater than 1 indicates a random distribution, whereas R = 0 indicates aggregation. Boundaries and sizes of home ranges varied seasonally for males, but not for females. Core areas were maintained as exclusive areas of activity; the sole exception was a male and female pair whose core areas overlapped slightly (<28.4%; Fig. It was our intention to gain new insights into the importance of variable spatial relationships in a solitary species. We measured the distribution of precincts (territories) on the study area using trapping data and behavioral observations. Six (54%) of the 11 animals radiotracked in both seasons maintained the same day burrows during the summer non-breeding and winter breeding seasons. We used the fixed kernel method because it has been shown to provide a less biased home-range area calculation than the adaptive kernel method (Kenward and Hodder 1996; Seaman and Powell 1996; Worton 1989). “They’re worth protecting, they’re worth appreciating. Space use in the nonbreeding season.—Home ranges of males and females were small, exclusive, and similar in size during the summer nonbreeding season. We suggest that flexible behavior in desert rodents may be a general response to the unpredictable conditions of an arid environment (Randall 1993; Randall, in press; Randall et al. During both the summer and winter tracking periods, we took 5 readings per animal per night, plus a daytime reading to locate each animal's burrow. During the breeding season, mating strategies in mammals often are influenced by a male's ability to monopolize reproductive females (Emlen and Oring 1977), and the distribution of females is viewed as a limiting resource (1ms 1988; Nelson 1995a; Ribble and Stanley 1998). = 16, P < 0.025) and the Monte Carlo 1,000 randomized locations (expected = 8.6 ± 0.1 m between neighbors; t = 3.76, d.f. We used 60% normal kernel isopleths to obtain core areas (presumed territories); we chose this percentage because it excluded outlying locations and thus produced a more stable core for analyses of spatial overlap between individuals. During the summer nonbreeding season, both males and females occupied territories of similar sizes that were located close to the core area of each animal's home range.

Overall, we found that D, ingens tolerates close associations with neighbors, but when neighboring precincts become available, these rodents demonstrate a preference for exclusive territories. We released all animals at the point of capture. We observed few aggressive encounters. During the summer season, 2 of these females had both their home ranges and core areas overlapped by a neighboring female (Table 1). Both values were close to 1, suggesting that animals are independently spaced. To understand more fully the social structure and mating behavior of D. ingens, we documented seasonal variation in home-range size and overlap by radiotracking animals during the breeding and nonbreeding seasons. Traps were baited with bird seed. Behavioral interactions consisted of males chasing each other away from the precincts of neighboring females (8 observations) and males following females into their burrows while exhibiting nasoanal contact (2 observations). We did not monitor reproduction condition while radiotracking these animals to avoid disturbing their natural spatial patterns. Clippix ETC: An online picture service of Florida's Educational Technology Clearinghouse . Les marsupiaux représentent près de la moitié des 230 espèces de mammifères d'Australie. comm.). Home ranges were calculated with a 95% distribution of data and overlap was estimated using 95% peeled polygons. Although D. ingens appears to tolerate close associations with neighbors, these rodents will readily move into neighboring precincts when these become available. Incremental analysis showed that approximately 60 locations were necessary for estimating home-range sizes for our sample. Home ranges of males overlapped by 30.2% ± 8.4% (n = 8 males) where they converged on neighboring territories of females (Fig. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. The nearest-neighbor analysis of Clark and Evans (1954) yielded R = 1.09; the Monte Carlo simulation (n = 1,000 randomized locations) produced R = 1.03. We used the fixed kernel method to establish core areas. We classified males as either scrotal (testes fully descended into scrotal sac) or nonscrotal (undescended testes). When data were not normally distributed, even after a log transformation, we used nonparametric Mann-Whitney U-tests and Wilcoxon signed-ranks tests. During the breeding season, home-range size of males increased significantly as mobility of males increased and home ranges expanded to overlap neighboring territories of females. In contrast, the core areas of 2 of 5 females overlapped by 35.1% ± 22.2% (Table 1). During the winter breeding season, which usually extends from January to May (Randall et al. The overlap matrices for both home ranges and core areas demonstrated that, although the outer ranges of 3 females overlapped extensively, their core areas remained separate and exclusive. After an individual was released from a trap, we visually followed the animal to its home precinct and recorded the location at which it entered a burrow. ); average home-range size during the week before the disappearance was 0.01 ± 0.00 ha versus 0.02 ± 0.00 ha during the week after disappearance (paired t = 0.534, n = 19, d.f. During the summer season, we obtained readings on alternate nights, from either dusk until midnight or midnight until dawn. If you are certain that you need such a large file, click the DOWNLOAD button to begin. Estimated home-range sizes and percentages of total home-range overlap among 7 animals, resident within 25 m of the female that disappeared from the study site. Based on 95% minimum convex polygons, home ranges of males (n = 8) averaged 0.10 ± 0.01 ha versus 0.02 ± 0.03 ha for home ranges of females (n = 9). We found no overlap between the home ranges of females. The findings appear in two new papers in Functional Ecology and the Biological Journal of the Linnean Society that present detailed analyses of the behaviors and biomechanics of both kangaroo rats and rattlesnakes.

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