Bushes protect tortoises from lethal overheating in arid areas of Morocco (original) (raw)
Related papers
How far can a tortoise walk in open habitat before overheating? Implications for conservation
Journal for Nature Conservation, 2014
Terrestrial chelonians are threatened worldwide by habitat destruction and illegal harvesting. Tortoises are slow moving animals susceptible to dehydration and overheating during movements in open habitats. Many species inhabit arid steppes where the availability of thermally buffered refuges (e.g. burrows) is a limiting factor. Determining the maximal distance between refuges that individuals can safely traverse during the active season is thus essential. We examined the relationship between body temperature variations and movement patterns in adult Testudo graeca in the arid steppes of Morocco. Using physical and mathematical models, our results suggest that during the active season adults cannot travel more than 1 km without serious risk of overheating. However, radio-tracking suggests that free-ranging individuals are behaviourally limited to 0.5 km trips between refuges. Overall, maintaining a distance less than 0.5 km between refuges (e.g. through bush planting) is essential to limit fragmentation and to retain healthy populations. This restoration would also benefit to many other species that depend on bush-refuges.
We used operative temperatures models shaped like tortoises to portray the operative thermal environment of desert tortoises (Gopherus morafkai) in three environments in Mexico during October 2012 – August 2013. Cooler, shadier thermal characteristics of tropical deciduous forest (TDF) in southern Sonora permit tortoise activity for ≈ 3X longer per day in forest than in coastal desertscrub, based on 12 days of comparative data in early October, and the effect is likely greater at hotter times of year. Induced buffelgrass (Pennisetum ciliare) pasture, which is the term used for created pasture in wildlands in Mexico) within the TDF biome was intermediate between these extremes, though more similar to desertscrub. Hours of thermally-imposed restriction of tortoise activity in pasture during March-August (6-10 hr/day) were far greater than in TDF (0.4-2.5 hr/day), although there was little effect in October, when we found tortoises in the pastures, which had warmer, more favorable temperatures for tortoise activity. “Sinaloan” tortoises in TDF are genetically divergent from Sonoran G. morafkai (Edwards et al., submitted), and may experience selection for a unique thermal physiology, but the Sinaloan genotype also occurs in very hot low-elevation thornscrub, which may constrain adaptation to the Te characteristics of TDF. The altered thermal regime of induced pastures poses a threat to desert tortoises in TDF and very likely in thornscrub, but conservation efforts permitting successional processes would likely allow both these biotic communities to restore a more favorable thermal environment for terrestrial turtles.
2021
The endangered Moorish tortoise Testudo graeca is the unique terrestrial chelonian species in North-west Africa. In west-central Morocco, the endemic subspecies, the Souss valley tortoise T. g. soussensis, occupies semi-arid to arid low-quality habitats, and is subject to serious threats. A long-term mark-recapture programme from 2001 to 2012 allowed estimating population size and structure, sex ratio, and survivorship in one of the well-known populations in a degraded and overgrazed arid steppe-land of west-central Morocco. Spring population size considerably decreased to more than half in less than 10 years, with a mean density lower than 3 ind.ha-1 in 2012 compared to its last known density estimat-ed in 2003. In spring 2012, the population structure exhibited an unbalanced male-biased sex ratio (61:39) and a scarcity of juveniles (<5%). We identified five major conservation problems in the study area: (i) habitat destruction and overgrazing; (ii) over-collecting of tortoises ...
– Agassiz's desert tortoise, Gopherus agassizii, faces threats from climate change. With limited mobility to move long distances to more-suitable habitat as climate change advances, whether protecting tortoises in situ or translocating them out of harm's way, a critical conservation task is identifying refugia, lands that will remain suitable under the current climate and the projected, end of the 21st Century warming and drying. While researchers have modeled tortoise habitat suitability, they have done so at coarse scales and did not identify climate refugia that may become apparent only with a fine-scale approach. It is at that scale that managers can implement measures that will foster habitat protection for tortoises throughout their current range. In this case study, we employed fine-scale habitat suitability modeling to identify current habitat and climate refugia within and surrounding the Marine Corps Air Ground Combat Center (MCAGCC) at Twentynine Palms, California. We modeled nearly 284,000 ha of currently suitable tortoise habitat within an 858,800-ha study area. Projected maximum end-of-the-century summer temperatures could reduce the area of tortoise habitat 55% to 127,650 ha; however, almost 115,800 ha would overlap current tortoise habitat and would serve as climate refugia. Applied elsewhere, where tortoise protection must be balanced with other land uses, this approach could increase the efficacy of conservation for this threatened species. Nevertheless, until validated with field studies, habitat suitability models represent hypotheses as to current and future distributions of appropriate tortoise habitat. These hypotheses should foster additional research identifying whether tortoise densities and demographic structure are more secure and whether tortoises can adapt to shifting climates more effectively within than outside modeled refugia.
Reptiles and Amphibians, 2018
The Souss Valley tortoise, Testudo graeca soussensis, is endemic to the semi-arid and arid low quality habitats of west central Morocco. Populations of this area are among the bestinvestigated populations in western Mediterranean. The long-term conservation of these declining populations is of particular management concern for this endemic and threatened subspecies. Here we present a data review on biological and ecological aspects of this subspecies dealing with morphology, distribution range and climatic niche, habitat use, food habits, activity cycle, and thermal responses to arid hot conditions, post-hatching growth, sexual maturity, sexual dimorphism, breeding ecology and demographics. After an analysis of the major threats on populations, we proposed management actions required to improve the conservation outcomes for this endangered tortoise in arid areas of west central Morocco. Conservation and restoration potentials of the declining populations and their habitat are also described, including habitat restoration and a captive breeding program.
Climatic variation and tortoise survival: Has a desert species met its match?
Biological Conservation, 2014
While demographic changes in short-lived species may be observed relatively quickly in response to climate changes, measuring population responses of long-lived species requires long-term studies that are not always available. We analyzed data from a population of threatened Agassiz's desert tortoises (Gopherus agassizii) at a 2.59 km 2 study plot in the Sonoran Desert ecosystem of Joshua Tree National Park, California, USA from 1978 to 2012 to examine variation in apparent survival and demography in this long-lived species. Transect-based, mark-recapture surveys were conducted in 10 of those years to locate living and dead tortoises. Previous modeling suggested that this area would become unsuitable as tortoise habitat under a warming and drying climate scenario. Estimated adult population size declined greatly from 1996 to 2012. The population appeared to have high apparent survival from 1978 to 1996 but apparent survival decreased from 1997 to 2002, concurrent with persistent drought. The best model relating apparent survivorship of tortoises P18 cm over time was based on a three year moving average of estimated winter precipitation. The postures and positions of a majority of dead tortoises found in 2012 were consistent with death by dehydration and starvation. Some live and many dead tortoises found in 2012 showed signs of predation or scavenging by mammalian carnivores. Coyote (Canis latrans) scats and other evidence from the site confirmed their role as tortoise predators and scavengers. Predation rates may be exacerbated by drought if carnivores switch from preferred mammalian prey to tortoises during dry years. Climate modeling suggests that the region will be subjected to even longer duration droughts in the future and that the plot may become unsuitable for continued tortoise survival. Our results showing wide fluctuations in apparent survival and decreasing tortoise density over time may be early signals of that possible outcome.
2009
Domaine vital automnal de tortues (Testudo hermanni) suivies par radio-pistage dans un environnement mediterraneen semi-aride. - La phase d'activite automnale est cruciale pour la plupart des reptiles europeens qui restent inactifs plusieurs mois durant l'hiver et qui doivent se preparer a cette periode de latence en orientant leurs activites vers l'acquisition de nourriture et de reserves energetiques. Neanmoins les caracteristiques ecologiques de cette phase d'activite automnale demeurent relativement inconnues pour la majorite des especes reptiliennes, y compris les cheloniens. Dans la presente etude nous avons suivi par radio-pistage quatre tortues (Testudo hermanni), deux mâles et deux femelles, durant la periode d'activite automnale afin de comprendre les patterns de deplacement et l'etendue des domaines vitaux. L'etude de terrain a ete conduite dans une zone mediterraneenne semi-aride du centre de l'Italie. Les domaines vitaux ont ete determine...
Journal of thermal biology
Understanding the relationships between environmental variables and wildlife activity is an important part of effective management. The desert tortoise (Gopherus agassizii), an imperiled species of arid environments in the southwest US, may have increasingly restricted windows for activity due to current warming trends. In summer 2013, we deployed 48 motion sensor cameras at the entrances of tortoise burrows to investigate the effects of temperature, sex, and day of the year on the activity of desert tortoises. Using generalized estimating equations, we found that the relative probability of activity was associated with temperature (linear and quadratic), sex, and day of the year. Sex effects showed that male tortoises are generally more active than female tortoises. Temperature had a quadratic effect, indicating that tortoise activity was heightened at a range of temperatures. In addition, we found significant support for interactions between sex and day of the year, and sex and te...
The diet and vegetation composition of Egyptian tortoise habitat in North Sinai, Egypt
Amphibia-reptilia, 2021
We studied the diet and vegetation composition of Egyptian tortoise, Testudo kleinmanni, habitat in North Sinai, Egypt. Dietary data was recorded through direct observations and the vegetation composition was recorded through the use of quadrats and line transects in 66 sampling points (33 in tortoise areas and 33 in non-tortoise areas). Our results showed that vegetation of Egyptian tortoise habitat had high species richness, Simpson’s diversity index, and vegetation cover in contrast to areas without Egyptian tortoises. These tortoises ate thirty four species of plants, a majority of these being perennials, with most feeding observations occurring in spring and winter. The consumption of perennials may enable Egyptian tortoises to find and consume food in an arid environment with low, variable and unpredictable rainfall. The plants most consumed were rare in our vegetation survey, suggesting food preferences. Our study suggests that Egyptian tortoises, which rely on vegetation for...
Amphibia-reptilia, 2023
A previous study on the feeding habits of Moorish tortoises in west-central Morocco suggests that these animals are selective herbivores, but the nutritional consequences have not been examined. Because of the potassium excretion load, which requires water and/or nitrogen loss, we predicted that tortoises do not have salt glands. Moorish tortoises prefer plants rich in water and protein but low in potassium (PEP index). To this end, we studied the spring diet of adult tortoises in an arid steppe in west-central Morocco during two seasons of relatively dry years (2011-2012) using feces analyses. We also estimated the relative abundance of potential food plants by stratified sampling under the canopy of jujube bushes Ziziphus lotus. We statistically compared diet to plant abundance. Finally, we assessed plant species' nutritional composition (water, crude protein, and potassium) available to tortoises. Results showed that species assemblages differed significantly between the two plant communities in both years. Nevertheless, tortoises consumed only about 5-6 and nearly the same species at the study site in 2011 and 2012, respectively. The plants consumed by the tortoises had the highest positive PEP index values indicating that there was more water and nitrogen in the food than is needed to excrete potassium.