Survival Rates and Causes of Mortality of Testudo graeca Hatchlings in Southwestern Spain

Keller, Claudia; Díaz‐Paniagua, Carmen; Andreu, Ana C.

doi:10.2307/1565303

Cited by 23 publications

(20 citation statements)

References 20 publications

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“…It might be relevant that three of our rainy years (1990, 1996 and 1997) were in the upper quartile of annual rainfall distribution in Dot'iana ( Fig. But the same circumstances likely favoured a higher energy investrnent in eggs, enhancing the prospects of embryo and early postemergence survival, which was found to be relatively low in this population during a dry period (Keller et al 1998). ), possibly compromising body condition of iemales in an important phase of energy allocation to egg maturation (first clutehes are laid in late March; Diaz-Paniagua et al 1996), Partial resorption of follicles in adverse conditions has been described for other tortoises Coe 1978, Rostal et al, 1994), However, the tendeney observed otherwise in T. graeea in Dofiana to keep a relatively constant reprodtictive output suggests that favourable environmental eonditions would not elicit a sufficient increase in feeandity to eause alone the 1992ae reeruitment peak.…”

Section: Environmental Influence On Demographic Traitsmentioning

confidence: 84%

Long-term demographic fluctuations of the spur-thighed tortoise Testudo graeca in SW Spain

Díaz‐Paniagua¹,

Keller²,

Andreu³

2001

Ecography

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We assessed the dynamics of a population of spur-lhighcd tortoises, Testudo graeea. placed under long-term protection from human interference. We estimated demographic parameters and constructed vertical lite tables based on age structures for two different study periods separated by a 12-yr interval. Average age at maturity was 6.9 yr for males and 8.5 yr for females. Clutch size varied with female size, but tended to be constant among years. Average annual female fecundity over 9 yr was 8.4 eggs and decreased significantly in years of high rainfall. Females seemed to reproduce yearly, but with a constantly low output, probabiy maximising both their long-term reproductive potential and Ihc probability of producing offspring during favourable years for hatchling survival. Adult survival was high and constant between periods. Juvenile survivorship from egg to 6 yr and recruitment into the 5-8-yr-old cohorts were significantly higher in the second period. Life tables indicated a predominantly negative demographic trend for the first period, with an average population increase rate of 0.977. and an overall positive tendency for the second period, with an average increase rate of 1,091, These figures suggest that the population experienced a variation that was closer to the maximum estimates for the tirst period, mediated mainly by an increase in juvenile recruitment. The data indicate that, besides high adult survival rates, occasional high juvenile recruitment bouts may have an important regulatory effect on the population dynamics of Testudo graeea.

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Section: Environmental Influence On Demographic Traitsmentioning

confidence: 84%

Long-term demographic fluctuations of the spur-thighed tortoise Testudo graeca in SW Spain

Díaz‐Paniagua¹,

Keller²,

Andreu³

2001

Ecography

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“…On the other hand, this time was generally shorter in juveniles than in adults (highly significant at Golem Grad). This suggests that juveniles rapidly attempted to find a shelter, probably because their soft shell and small size provide limited protection against the predators (Douglass & Winegraner, ; Keller, Diaz‐Paniagua & Andreu, ). We also found differences in the amount of time during which the tortoises tried to find an alternative before walking off the ledge.…”

Section: Discussionmentioning

confidence: 99%

Moving in the real world: tortoises take the plunge to cross steep steps

Golubović

Arsovski

Ajtić

et al. 2013

Biol J Linn Soc Lond

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Despite exhibiting low velocity and limited agility, many tortoises undertake large scale movements and must overcome various obstacles, notably in populations living in hilly or rocky habitats. Although crucial, studies exploring how tortoises move in complex and irregular environments are scarce. In this context, we examined an important behavioural trait: how tortoises (Testudo hermanni) deal with step‐like obstacles. In their natural habitat, individuals were positioned in a challenging situation: they were placed on a bench approximately 50 cm high, and were observed over a 10‐min period. We compared the behaviour of the tortoises (taking a risk to ‘jump’ or waiting) from two populations living in contrasted habitats: flat versus rugged (crisscrossed by cliffs and rocky steps). Individuals from the flat habitat were reluctant to jump, whereas most tortoises from the rugged habitat jumped. Immature tortoises were less willing to jump compared to larger and more experienced adults. These results suggest that challenging habitats increase boldness. In addition to fundamental findings, these results may have conservation value and assist in improving translocation strategies for endangered tortoise populations. © 2013 The Linnean Society of London

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“…Recent data from Testudo graeca, which has several similarities in life history and ecology with G. berlandieri, provide provocative evidence that survival from the nest to 1 yr of age is in the range necessary to maintain a population. In a Spanish population, hatching success was 82.4% and hatchling survival was 0.39, indicating 32% survival from egg laying through the first winter (Diaz-Paniagua et al 1997, Keller et al 1998. Nest predation was absent in a Greek population of T. hermanni, a related species (Swingland and Stubbs 1985).…”

Section: Recruitmentmentioning

confidence: 96%

“…In a Spanish population, hatching success was 82.4% and hatchling survival was 0.39, indicating 32% survival from egg laying through the first winter (Diaz-Paniagua et al 1997, Keller et al 1998). In a Spanish population, hatching success was 82.4% and hatchling survival was 0.39, indicating 32% survival from egg laying through the first winter (Diaz-Paniagua et al 1997, Keller et al 1998).…”

Section: Recruitmentmentioning

confidence: 99%

Variation in Tortoise Life History: Demography of Gopherus berlandieri

Hellgren¹,

Kazmaier²,

Ruthven³

et al. 2000

Ecology

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Turtles provide excellent models for studies of life history strategies, but terrestrial species are underrepresented in these analyses. We present a life table and demographic parameters of an inland population of Gopherus berlandieri to contribute to the study of evolution of turtle life histories. Data were gathered during a mark-recapture and radiotelemetry study in the Tamaulipan Biotic Province in southern Texas, USA. A total of 835 individuals were captured, measured, and their ages estimated. Females matured at 131 mm carapace length at an average of 5 yr of age (range: 4-8 yr). Clutch size, as determined by ultrasound, averaged 2.07 ?+ 0.15 eggs (n = 49). No nests were found, and we estimated clutch frequency with a quadratic model to be 1.34 clutches-female-t-year-1. Survival was estimated from age frequency regression and telemetry. Annual male survival (0.828, 0.834) differed (P < 0.05) from female survival (0.728, 0.774) for both techniques of estimation. Age-specific female survival ranged from 0.62 to 0.83 for 5-to 15-yr-old tortoises. Differential mortality of sexes led to a male-biased sex ratio in older age classes. Age structures of captured individuals did not vary (P > 0.05) among years, and population estimates did not differ among years; therefore, we constructed a life table under the assumption of a stationary population (r = 0.0). Under this assumption, survival from nest to age 4 yr must be at least 0.245, with hatchling survival of 0.528 to maintain a stationary population. Gopherus berlandieri matured at an earlier age, had smaller clutch sizes, and exhibited lower rates of female survival than other Gopherus species. We propose a physiological mechanism for lower female survival that implies trade-offs among egg size, subsequent hatchling survival, and female health. We maintain that high hatchling survival is necessary for population persistence. In an evolutionary context, we theorize that the selective advantages of small size and the life history strategies of G. berlandieri have been and are critical to its persistence.

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Survival Rates and Causes of Mortality of Testudo graeca Hatchlings in Southwestern Spain

Cited by 23 publications

References 20 publications

Long-term demographic fluctuations of the spur-thighed tortoise Testudo graeca in SW Spain

Long-term demographic fluctuations of the spur-thighed tortoise Testudo graeca in SW Spain

Moving in the real world: tortoises take the plunge to cross steep steps

Variation in Tortoise Life History: Demography of Gopherus berlandieri

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