Home Range Size and Movements by Desert Tortoises, Gopherus agassizii, in the Eastern Mojave Desert

O’Connor, Michael; Zimmerman, Linda C.; Ruby, Douglas E.; Bulova, Susan J.; Spotila, James R.

doi:10.2307/1467070

Cited by 51 publications

(48 citation statements)

References 20 publications

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“…Large home ranges appear to characterise the larger Testudinidae species (e.g., Geochelone (Hailey and Coulson 1996;Smith et al 1999)), as well as the desert species (e.g., Testudo kleinmanii (Geffen and Mendelssohn 1988) and Gopherus agassizii (Burge 1977;Barret 1990;O'Connor et al 1994; this study)). A large home range of desert-dwelling tortoises may reflect the paucity of feeding resources (Geffen and Mendelssohn 1988).…”

Section: Discussionmentioning

confidence: 56%

“…The result is a marked decrease of locomotor activity and a reduction in their home range. Such a shift has been documented in many other species (Chelazzi and Francisci 1979;McRae et al 1981;Geffen and Mendelssohn 1988;Calzolai and Chelazzi 1991;Diemer 1992;O'Connor et al 1994;Diaz-Paniagua et al 1995;Weatherby 1995;Jones 1996).…”

Section: Males Intensively Patrol Their Territorymentioning

confidence: 73%

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Sex divergence in space utilisation in the steppe tortoise (Testudo horsfieldi)

Lagarde¹,

Bonnet²,

Henen³

et al. 2003

Can. J. Zool.

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Abstract:In animal species without parental care, the fitness of males should increase with the number of females encountered, court, and fertilise, and the fitness of females depends strongly on the quantity and quality of resources acquired. This should translate into a marked sex differences in the patterns of space utilisation. We analysed the sex divergences in home range and movements pattern in the steppe tortoise (Testudo horsfieldi) in Uzbekistan. From the radio-tracking data of 36 individuals throughout the active season, the home range of the male steppe tortoise was estimated to be smaller than that of the female (24 vs. 57 ha), even when the analysis focused on the mating season only. During the mating season, males intensively patrolled a small area, going back and forth within their territory, thereby covering greater distances than females. The females movements were more unidirectional, resulting in large loops over a very extended home range. We proposed several nonexclusive hypothesis for such a pattern.Résumé : Chez de nombreuses espèces animales dépourvues de soins parentaux, le succès reproducteur des mâles dépend du nombre de femelles qu'ils rencontrent, courtisent et parviennent à féconder et celui des femelles dépend fortement de la qualité et de la quantité des ressources trophiques qu'elles acquièrent. Cela se traduit souvent par des différences marquées dans les modes d'occupation de l'espace développés par chaque sexe. Dans cette étude, nous analysons les divergences sexuelles dans les domaines vitaux et les déplacements chez la tortue des steppes (Testudo horsfieldi) en Ouzbékistan. A partir d'un suivi par radio-tracking de 36 individus tout au long de la saison d'activité, le domaine vital des mâles s'est avéré plus petit que celui des femelles (24 contre 57 ha), même lorsque l'analyse est restreinte à la période d'accouplements. Ce résultat surprenant est partiellement clarifié lorsque la nature des déplacements est prise en compte. Durant la saison des accouplements, les mâles patrouillent intensivement un petit domaine vital, en réalisant de constants allers et retours, parcourant de plus grandes distances que les femelles. Les femelles réalisent de plus petits déplacements quotidiens, s'enchaînant en de larges boucles couvrant un domaine vital étendu. Différentes hypothèses non exclusives sont proposées pour expliquer ce pattern d'occupation de l'espace.

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Section: Discussionmentioning

confidence: 56%

Section: Males Intensively Patrol Their Territorymentioning

confidence: 73%

Sex divergence in space utilisation in the steppe tortoise (Testudo horsfieldi)

Lagarde¹,

Bonnet²,

Henen³

et al. 2003

Can. J. Zool.

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“…First, females were more likely than males to be killed by coyotes. This was counter to what might be expected, as male tortoises are known to have larger home ranges (Berry 1986, O'Connor et al 1994, Harless et al 2009) and generally move greater distances, especially after translocation (Nussear 2004, Field et al 2007). Elevated female mortality has been reported elsewhere (SAIC 1993, Field et al 2007, and Riedle et al (2010) found higher mortality among female than among male desert tortoises at a Sonoran Desert site.…”

Section: Discussionmentioning

confidence: 72%

Effects of subsidized predators, resource variability, and human population density on desert tortoise populations in the Mojave Desert, USA

Esque¹,

Nussear²,

Drake³

et al. 2010

Endang. Species. Res.

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Understanding predator-prey relationships can be pivotal in the conservation of species. For 2 decades, desert tortoise Gopherus agassizii populations have declined, yet quantitative evidence regarding the causes of declines is scarce. In 2005, Ft. Irwin National Training Center, California, USA, implemented a translocation project including 2 yr of baseline monitoring of desert tortoises. Unusually high predation on tortoises was observed after translocation occurred. We conducted a retrospective analysis of predation and found that translocation did not affect the probability of predation: translocated, resident, and control tortoises all had similar levels of predation. However, predation rates were higher near human population concentrations, at lower elevation sites, and for smaller tortoises and females. Furthermore, high mortality rates were not limited to the National Training Center. In 2008, elevated mortality (as high as 43%) occurred throughout the listed range of the desert tortoise. Although no temporal prey base data are available for analysis from any of the study sites, we hypothesize that low population levels of typical coyote Canis latrans prey (i.e. jackrabbits Lepus californicus and other small animals) due to drought conditions influenced high predation rates in previous years. Predation may have been exacerbated in areas with high levels of subsidized predators. Many historical reports of increased predation, and our observation of a rangewide pattern, may indicate that high predation rates are more common than generally considered and may impact recovery of the desert tortoise throughout its range.

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“…Male desert tortoises might be expected to have high FMRs throughout most of the warm seasons because their home ranges are much larger than those of females (Berry 1986;O'Connor et al 1994), and males court and attempt to mate with females at any opportunity (Rostal et al 1994;Ruby and Niblick 1994;personal observations). Female desert tortoises do not appear to actively seek mates, and thus probably expend less energy in courtship and mating than males.…”

Section: Sex Eectsmentioning

confidence: 99%

Effects of climatic variation on field metabolism and water relations of desert tortoises

et al. 1998

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We used the doubly labeled water method to measure the field metabolic rates (FMRs, in kJ kgday) and water flux rates (WIRs, in ml HO kgday) of adult desert tortoises (Gopherus agassizii) in three parts of the Mojave Desert in California over a 3.5-year period, in order to develop insights into the physiological responses of this threatened species to climate variation among sites and years. FMR, WIR, and the water economy index (WEI, in ml HO kJ, an indicator of drinking of free water) differed extensively among seasons, among study sites, between sexes, and among years. In high-rainfall years, males had higher FMRs than females. Average daily rates of energy and water use by desert tortoises were extraordinarily variable: 28-fold differences in FMR and 237-fold differences in WIR were measured. Some of this variation was due to seasonal conditions, with rates being low during cold winter months and higher in the warm seasons. However, much of the variation was due to responses to year-to-year variation in rainfall. Annual spring peaks in FMR and WIR were higher in wet years than in drought years. Site differences in seasonal patterns were apparently due to geographic differences in rainfall patterns (more summer rain at eastern Mojave sites). In spring 1992, during an El Niño (ENSO) event, the WEI was greater than the maximal value obtainable from consuming succulent vegetation, indicating copious drinking of rainwater at that time. The physiological and behavioral flexibility of desert tortoises, evident in individuals living at all three study sites, appears central to their ability to survive droughts and benefit from periods of resource abundance. The strong effects of the El Niño (ENSO) weather pattern on tortoise physiology, reproduction, and survival elucidated in this and other studies suggest that local manifestations of global climate events could have a long-term influence on the tortoise populations in the Mojave Desert.

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Home Range Size and Movements by Desert Tortoises, Gopherus agassizii, in the Eastern Mojave Desert

Cited by 51 publications

References 20 publications

Sex divergence in space utilisation in the steppe tortoise (Testudo horsfieldi)

Sex divergence in space utilisation in the steppe tortoise (Testudo horsfieldi)

Effects of subsidized predators, resource variability, and human population density on desert tortoise populations in the Mojave Desert, USA

Effects of climatic variation on field metabolism and water relations of desert tortoises

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