D. Ruby, W. B. Jennings, G. Goodlett, J. Spotila, H. Mushinsky
Abstract. In a study to reduce Mojave Desert Tortoise (Gopherus agassizii) mortality along roadways, we tested the feasibility of structures that discourage tortoises from 1) walking or “pacing” along barriers or 2) crossing areas where gates or openings occur. The diversion designs we tested (one straight and one curved structure, each 7.6 m long) deflected tortoises away from fences at nearly the same rate as tortoises who continued walking along barriers despite the diversion (36.8% vs. 35.7%). No “tortoise guard” structures that we tested, similar to cattle guard structures, were 100% effective at preventing tortoises from crossing the opening. We identified essential characteristics of an effective “tortoise guard” such as minimum gap sizes in the structure and a construction design that allowed a tortoise to climb out of a trench under the structure.
{"title":"Experimental Designs for Tortoise Pacing Diversion Structures and Tortoise Guards Along Highway Barriers","authors":"D. Ruby, W. B. Jennings, G. Goodlett, J. Spotila, H. Mushinsky","doi":"10.2744/CCB-1534.1","DOIUrl":"https://doi.org/10.2744/CCB-1534.1","url":null,"abstract":"Abstract. In a study to reduce Mojave Desert Tortoise (Gopherus agassizii) mortality along roadways, we tested the feasibility of structures that discourage tortoises from 1) walking or “pacing” along barriers or 2) crossing areas where gates or openings occur. The diversion designs we tested (one straight and one curved structure, each 7.6 m long) deflected tortoises away from fences at nearly the same rate as tortoises who continued walking along barriers despite the diversion (36.8% vs. 35.7%). No “tortoise guard” structures that we tested, similar to cattle guard structures, were 100% effective at preventing tortoises from crossing the opening. We identified essential characteristics of an effective “tortoise guard” such as minimum gap sizes in the structure and a construction design that allowed a tortoise to climb out of a trench under the structure.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116210469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. We began developing our Geometric Tortoise Ecosystem Preserve in 2015. At the same time, we began a mark–recapture study to detect changes in the population size through time to inform our management practices. We now have data through 2021. Mark–recapture analysis gives a population size of between 800 and 1200 individuals. It is the last remaining substantial population. Using Lande's classification of 1933 of stochastic influences on demography, we find that 1) demographic stochasticity is not a problem, as the population is large enough and consists of individuals whose home ranges overlap; 2) environmental stochasticity is important mainly through variations in annual rainfall, including severe droughts; and 3) catastrophes occur in the form of wildfire that can destroy a local population. Taken together, these environmental effects can cause large changes in population size, making this species at risk of local extinction. If it were to go extinct, there are no other adjacent populations that could be used to recolonize our preserve. Therefore, we conclude that head starting is necessary to safeguard the population.
{"title":"Management of a Geometric Tortoise (Psammobates geometricus) Population in a High-Risk, Fire-Prone Landscape","authors":"A. Kiester, J. Juvik, E. Baard, M. Hofmeyr","doi":"10.2744/CCB-1571.1","DOIUrl":"https://doi.org/10.2744/CCB-1571.1","url":null,"abstract":"Abstract. We began developing our Geometric Tortoise Ecosystem Preserve in 2015. At the same time, we began a mark–recapture study to detect changes in the population size through time to inform our management practices. We now have data through 2021. Mark–recapture analysis gives a population size of between 800 and 1200 individuals. It is the last remaining substantial population. Using Lande's classification of 1933 of stochastic influences on demography, we find that 1) demographic stochasticity is not a problem, as the population is large enough and consists of individuals whose home ranges overlap; 2) environmental stochasticity is important mainly through variations in annual rainfall, including severe droughts; and 3) catastrophes occur in the form of wildfire that can destroy a local population. Taken together, these environmental effects can cause large changes in population size, making this species at risk of local extinction. If it were to go extinct, there are no other adjacent populations that could be used to recolonize our preserve. Therefore, we conclude that head starting is necessary to safeguard the population.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114348722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Ruby, W. B. Jennings, G. Goodlett, J. Spotila, H. Mushinsky
Abstract. We investigated methods for reducing highway-caused mortality of Mojave Desert Tortoises (Gopherus agassizii) using barriers at the Desert Tortoise Conservation Center, located near Las Vegas, Nevada. Experiments tested effectiveness of various barriers of different heights and made of different construction materials, sex-dependent behaviors including rate of escapes, appropriate height of a barrier, and adverse effects on other sympatric vertebrate species including potential entrapment. Informed by analyzing previous investigations, we tested captive adult desert tortoises (midline carapace length ≥ 180 mm) within enclosures made from 8 different common construction materials, quantified behavioral responses of individuals over several (4–14) days, and identified sex-dependent responses to these barriers. Both sexes pushed against see-through barriers more than solid barriers (58% males, 67% females) and males reversed direction of pacing more often than females (56%). Pen escapes related to pacing reversals and were generally by males. Direction reversals and escapes occurred mostly with wire mesh designs and low (20-cm) solid barriers. Frequency of body contact was not linearly correlated with larger mesh sizes. Solid barriers appear to offer the best deterrent but are more expensive. Animals that escaped in trials lasting several days were larger than average size and often escaped more than once. Tortoises escaped at weak points in barriers, such as gaps with the ground, pen corners, breaks in material, or by climbing over the barrier. In testing minimum effective barrier height for 3 types of barrier materials, none climbed over at 46 cm, 5 climbed over at 30 cm, and 19 others climbed over at lower heights. We observed native species interactions with our barrier enclosures (n = 70) and compared morphometric measurements of common desert reptiles vs. barrier dimensions. These data suggested that different barrier types preferentially affect specific sizes of animals although we observed no mortality. While solid barriers stop all reptiles, wire meshes entrap reptile species smaller than mesh size (such as Callisaurus draconoides and Uta stansburiana) and stop larger species (such as Dipsosaurus dorsalis and Coluber flagellum). Morphometric measures of juvenile tortoises indicated that they could pass through the 2 largest wire mesh sizes we tested.
{"title":"Design of Roadway Barriers to Reduce Desert Tortoise Mortality on Paved Road Infrastructure","authors":"D. Ruby, W. B. Jennings, G. Goodlett, J. Spotila, H. Mushinsky","doi":"10.2744/CCB-1533.1","DOIUrl":"https://doi.org/10.2744/CCB-1533.1","url":null,"abstract":"Abstract. We investigated methods for reducing highway-caused mortality of Mojave Desert Tortoises (Gopherus agassizii) using barriers at the Desert Tortoise Conservation Center, located near Las Vegas, Nevada. Experiments tested effectiveness of various barriers of different heights and made of different construction materials, sex-dependent behaviors including rate of escapes, appropriate height of a barrier, and adverse effects on other sympatric vertebrate species including potential entrapment. Informed by analyzing previous investigations, we tested captive adult desert tortoises (midline carapace length ≥ 180 mm) within enclosures made from 8 different common construction materials, quantified behavioral responses of individuals over several (4–14) days, and identified sex-dependent responses to these barriers. Both sexes pushed against see-through barriers more than solid barriers (58% males, 67% females) and males reversed direction of pacing more often than females (56%). Pen escapes related to pacing reversals and were generally by males. Direction reversals and escapes occurred mostly with wire mesh designs and low (20-cm) solid barriers. Frequency of body contact was not linearly correlated with larger mesh sizes. Solid barriers appear to offer the best deterrent but are more expensive. Animals that escaped in trials lasting several days were larger than average size and often escaped more than once. Tortoises escaped at weak points in barriers, such as gaps with the ground, pen corners, breaks in material, or by climbing over the barrier. In testing minimum effective barrier height for 3 types of barrier materials, none climbed over at 46 cm, 5 climbed over at 30 cm, and 19 others climbed over at lower heights. We observed native species interactions with our barrier enclosures (n = 70) and compared morphometric measurements of common desert reptiles vs. barrier dimensions. These data suggested that different barrier types preferentially affect specific sizes of animals although we observed no mortality. While solid barriers stop all reptiles, wire meshes entrap reptile species smaller than mesh size (such as Callisaurus draconoides and Uta stansburiana) and stop larger species (such as Dipsosaurus dorsalis and Coluber flagellum). Morphometric measures of juvenile tortoises indicated that they could pass through the 2 largest wire mesh sizes we tested.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125491296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. This study examined population ecology parameters for a southern population of the tent tortoise (Psammobates tentorius tentorius) in the Karoo. We found a relatively low density of tortoises (49 tortoises/km2) skewed to adults with a 1:1 sex ratio. The tortoises' contrasting dark and light carapacial patterns create crypsis with the disruptive shadows cast at the base of vegetation (mostly shrubs) where the tortoises seek refuge. The largest female was 14.7 cm, which makes her approximately 42 yrs old. The largest male was 11.6 cm, which makes him approximately 42 yrs old. We can distinguish males and females at carapace lengths of approximately 8–10 cm, when the tortoises are approximately 8–10 yrs old. Psammobates t. tentorius is a sexually size-dimorphic species in which adult females are significantly larger than are males. Selection for body shape and size appears attributable to fitness between the sexes (e.g., egg production and size in females, and opportunities to mate by males). We characterize this first group of nominate tent tortoises for future comparisons with other population. The study provides critical baseline information for the long-term management and conservation of this species, and adds to our understanding of the fauna of the Succulent Karoo.
{"title":"Population Structure and Sexual Dimorphism in a Southern Population of Tent Tortoises (Psammobates tentorius tentorius) of the Karoo, South Africa","authors":"T. Leuteritz, M. Hofmeyr","doi":"10.2744/CCB-1566.1","DOIUrl":"https://doi.org/10.2744/CCB-1566.1","url":null,"abstract":"Abstract. This study examined population ecology parameters for a southern population of the tent tortoise (Psammobates tentorius tentorius) in the Karoo. We found a relatively low density of tortoises (49 tortoises/km2) skewed to adults with a 1:1 sex ratio. The tortoises' contrasting dark and light carapacial patterns create crypsis with the disruptive shadows cast at the base of vegetation (mostly shrubs) where the tortoises seek refuge. The largest female was 14.7 cm, which makes her approximately 42 yrs old. The largest male was 11.6 cm, which makes him approximately 42 yrs old. We can distinguish males and females at carapace lengths of approximately 8–10 cm, when the tortoises are approximately 8–10 yrs old. Psammobates t. tentorius is a sexually size-dimorphic species in which adult females are significantly larger than are males. Selection for body shape and size appears attributable to fitness between the sexes (e.g., egg production and size in females, and opportunities to mate by males). We characterize this first group of nominate tent tortoises for future comparisons with other population. The study provides critical baseline information for the long-term management and conservation of this species, and adds to our understanding of the fauna of the Succulent Karoo.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116981441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Chatfield, Gregory LeClair, Hunter J. Howell, Cheryl A. Frederick
Abstract. The wood turtle (Glyptemys insculpta) is experiencing widespread declines throughout its range in the eastern United States and Canada. Maine has been considered a stronghold for the species due to an abundance of suitable upland and stream habitat. Furthermore, recent studies have identified Maine as a potentially important climate refuge for wood turtles. Using data collected in a 5-yr capture–mark–recapture study on a wood turtle population in central Maine, we estimate population size, apparent survival rates, population growth rates, and population viability. We also performed a sensitivity analysis to illustrate the impacts of slight perturbations to demographic rates. Our estimated total population size is 73 (95% CI = 69–85) individuals. Annual apparent survival varied across years, ranging from 80.5% to 97.5%, with females having a slightly higher survival at 94.9% (95% CI = 81.6%–97.8%) than males at 92.8% (95% CI = 77.6%–97.4%). The baseline population viability analysis model predicted a k of 0.93 (95% CI = 0.91–0.95) and a 100% probability of extinction within 150 yrs. Despite some broad permutations in our baseline demographic parameters, there were no scenarios included within our sensitivity analysis that increased the population's growth rate to a positive value. These results have implications for the long-term persistence of wood turtles in Maine and throughout their range. Our study helps fill a need for current data from this area that may be used to inform both local and regional management plans.
摘要木龟(Glyptemys insculpta)在美国东部和加拿大的分布范围内正经历着广泛的衰退。缅因州一直被认为是该物种的据点，因为有丰富的合适的高地和溪流栖息地。此外，最近的研究已经确定缅因州是木龟潜在的重要气候避难所。利用在缅因州中部对木龟种群进行的为期5年的捕获-标记-再捕获研究中收集的数据，我们估计了种群规模、表观存活率、种群增长率和种群活力。我们还进行了敏感性分析，以说明轻微扰动对人口统计率的影响。我们估计总种群规模为73 (95% CI = 69-85)。年表观生存率各年不同，从80.5%到97.5%不等，其中女性的生存率为94.9% (95% CI = 81.6%-97.8%)略高于男性的92.8% (95% CI = 77.6%-97.4%)。基线种群活力分析模型预测k为0.93 (95% CI = 0.91-0.95)， 150年内灭绝的概率为100%。尽管我们的基线人口统计参数中有一些广泛的排列，但在我们的敏感性分析中没有包括将人口增长率提高到正值的情景。这些结果对缅因州的木龟及其整个活动范围的长期持久性有影响。我们的研究有助于填补对该地区当前数据的需求，这些数据可用于为当地和区域管理计划提供信息。
{"title":"Demography and Viability of a Central Maine Population of Wood Turtles (Glyptemys insculpta)","authors":"M. Chatfield, Gregory LeClair, Hunter J. Howell, Cheryl A. Frederick","doi":"10.2744/CCB-1548.1","DOIUrl":"https://doi.org/10.2744/CCB-1548.1","url":null,"abstract":"Abstract. The wood turtle (Glyptemys insculpta) is experiencing widespread declines throughout its range in the eastern United States and Canada. Maine has been considered a stronghold for the species due to an abundance of suitable upland and stream habitat. Furthermore, recent studies have identified Maine as a potentially important climate refuge for wood turtles. Using data collected in a 5-yr capture–mark–recapture study on a wood turtle population in central Maine, we estimate population size, apparent survival rates, population growth rates, and population viability. We also performed a sensitivity analysis to illustrate the impacts of slight perturbations to demographic rates. Our estimated total population size is 73 (95% CI = 69–85) individuals. Annual apparent survival varied across years, ranging from 80.5% to 97.5%, with females having a slightly higher survival at 94.9% (95% CI = 81.6%–97.8%) than males at 92.8% (95% CI = 77.6%–97.4%). The baseline population viability analysis model predicted a k of 0.93 (95% CI = 0.91–0.95) and a 100% probability of extinction within 150 yrs. Despite some broad permutations in our baseline demographic parameters, there were no scenarios included within our sensitivity analysis that increased the population's growth rate to a positive value. These results have implications for the long-term persistence of wood turtles in Maine and throughout their range. Our study helps fill a need for current data from this area that may be used to inform both local and regional management plans.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131305058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Bu, Jian Wang, Liu Lin, Jichao Wang, F. Xiao, H. Shi
Abstract. In China, Hainan Island is a priority area for turtle conservation because of its biodiversity. Over the years, errors in turtle taxonomy and distribution have been made in the scientific literature, perpetuating into relevant laws and government documents and affecting conservation and management. In the present article, we describe the species of nonmarine turtles on Hainan Island, China, based on literature, museum specimens, and field surveys during the past 27 yrs. Historically, 23 nonmarine turtle species were recorded on Hainan Island. Among them, 9 species should be removed due to errors: 5 species are not naturally distributed on Hainan Island (Manouria impressa, Sacalia bealei, Cuora flavomarginata, Mauremys nigricans, and Mauremys reevesii), 3 are invalid hybrids (Ocadia philippeni, Sacalia pseudocellata, and Cuora serrata), and 1 is a synonym of another species (Mauremys megalocephala is a synonym of M. reevesii). In addition, of the 3 new species recorded from Hainan Island (Sacalia insulensis, Pelodiscus variegatus, and Pelodiscus parviformis), S. insulensis replaces Sacalia quadriocellata, P. variegatus is valid, and P. parviformis is likely an error. Therefore, there should be 12 nonmarine turtle species naturally found on Hainan Island: Platysternon megacephalum, Cuora galbinifrons, Cuora mouhotii, Cuora trifasciata, Geoemyda spengleri, Mauremys mutica, Mauremys sinensis, S. insulensis, Palea steindachneri, Pelochelys cantorii, Pelodiscus sinensis, and P. variegatus. Clarifying the presence and distribution of nonmarine turtle species will provide a reference for future research and practical guidance for conservation management on this turtle-rich island.
{"title":"Annotated Checklist of Nonmarine Turtles of Hainan Island, China","authors":"R. Bu, Jian Wang, Liu Lin, Jichao Wang, F. Xiao, H. Shi","doi":"10.2744/CCB-1547.1","DOIUrl":"https://doi.org/10.2744/CCB-1547.1","url":null,"abstract":"Abstract. In China, Hainan Island is a priority area for turtle conservation because of its biodiversity. Over the years, errors in turtle taxonomy and distribution have been made in the scientific literature, perpetuating into relevant laws and government documents and affecting conservation and management. In the present article, we describe the species of nonmarine turtles on Hainan Island, China, based on literature, museum specimens, and field surveys during the past 27 yrs. Historically, 23 nonmarine turtle species were recorded on Hainan Island. Among them, 9 species should be removed due to errors: 5 species are not naturally distributed on Hainan Island (Manouria impressa, Sacalia bealei, Cuora flavomarginata, Mauremys nigricans, and Mauremys reevesii), 3 are invalid hybrids (Ocadia philippeni, Sacalia pseudocellata, and Cuora serrata), and 1 is a synonym of another species (Mauremys megalocephala is a synonym of M. reevesii). In addition, of the 3 new species recorded from Hainan Island (Sacalia insulensis, Pelodiscus variegatus, and Pelodiscus parviformis), S. insulensis replaces Sacalia quadriocellata, P. variegatus is valid, and P. parviformis is likely an error. Therefore, there should be 12 nonmarine turtle species naturally found on Hainan Island: Platysternon megacephalum, Cuora galbinifrons, Cuora mouhotii, Cuora trifasciata, Geoemyda spengleri, Mauremys mutica, Mauremys sinensis, S. insulensis, Palea steindachneri, Pelochelys cantorii, Pelodiscus sinensis, and P. variegatus. Clarifying the presence and distribution of nonmarine turtle species will provide a reference for future research and practical guidance for conservation management on this turtle-rich island.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132668776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Chersina angulata females ovulate sequentially and oviposit multiple, mostly single egg clutches from early autumn (March) throughout winter and spring until early summer (December). No matter when eggs are laid, they usually hatch in autumn (March/April). Evidence based on circumstantial observations also demonstrates that wild and captive females occasionally retain the last clutch of the season until completion of embryonic development in autumn, conforming to the accepted definition of viviparity in reptiles. However, developmental progress throughout the year and embryonic stages of freshly deposited last clutches has not yet been reported. We candled all eggs laid from April to December in a captive colony of C. angulata in an outdoor enclosure in Cape Town, South Africa, to estimate developmental progress and embryonic stages. In all eggs laid during autumn, winter, and early spring (March to mid-October), vitelline blood vessels, indicating development had progressed to somite formation, only started to become visible at approximately the same time in late November. Until mid-spring, embryonic development of those eggs had been arrested prior to somite formation; the embryos underwent diapause until, presumably, increasing temperatures reinitiated development. Development then progressed throughout summer until the hatching stage was reached in early autumn. However, eggs laid in late spring (mid-October to November) skipped diapause, and embryonic development progressed without interruption, demonstrating that, depending on the season of oviposition, diapause in C. angulata is facultative. Candling of an egg laid in late December showed that, prior to oviposition, embryonic development inside the female had already advanced to an embryonic stage with well-developed vitelline circulation corresponding to Yntema stage 12. Contrary to the generally accepted wisdom that intrauterine embryonic development in the order Testudines is always arrested at the gastrula stage, embryonic development inside the female had already reached the stage of somite formation. This phenotypic plasticity in the expression or abolishment of preovipositional developmental arrest represents a transitional stage in the evolution towards viviparity.
{"title":"Facultative Embryonic Diapause and a Transitional Stage Between Oviparity and Viviparity in the South African Tortoise Chersina angulata","authors":"G. Kuchling, M. Hofmeyr","doi":"10.2744/CCB-1567.1","DOIUrl":"https://doi.org/10.2744/CCB-1567.1","url":null,"abstract":"Abstract. Chersina angulata females ovulate sequentially and oviposit multiple, mostly single egg clutches from early autumn (March) throughout winter and spring until early summer (December). No matter when eggs are laid, they usually hatch in autumn (March/April). Evidence based on circumstantial observations also demonstrates that wild and captive females occasionally retain the last clutch of the season until completion of embryonic development in autumn, conforming to the accepted definition of viviparity in reptiles. However, developmental progress throughout the year and embryonic stages of freshly deposited last clutches has not yet been reported. We candled all eggs laid from April to December in a captive colony of C. angulata in an outdoor enclosure in Cape Town, South Africa, to estimate developmental progress and embryonic stages. In all eggs laid during autumn, winter, and early spring (March to mid-October), vitelline blood vessels, indicating development had progressed to somite formation, only started to become visible at approximately the same time in late November. Until mid-spring, embryonic development of those eggs had been arrested prior to somite formation; the embryos underwent diapause until, presumably, increasing temperatures reinitiated development. Development then progressed throughout summer until the hatching stage was reached in early autumn. However, eggs laid in late spring (mid-October to November) skipped diapause, and embryonic development progressed without interruption, demonstrating that, depending on the season of oviposition, diapause in C. angulata is facultative. Candling of an egg laid in late December showed that, prior to oviposition, embryonic development inside the female had already advanced to an embryonic stage with well-developed vitelline circulation corresponding to Yntema stage 12. Contrary to the generally accepted wisdom that intrauterine embryonic development in the order Testudines is always arrested at the gastrula stage, embryonic development inside the female had already reached the stage of somite formation. This phenotypic plasticity in the expression or abolishment of preovipositional developmental arrest represents a transitional stage in the evolution towards viviparity.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130729683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Chersina angulata egg retention times differ among sequentially ovulated eggs from February to November, being shorter in eggs ovulated in October and November than in eggs ovulated in February, April, May, and July. More time is required to achieve eggshell calcification from July to October than from March to June. In most instances (71%) females lay their eggs when the eggshell still appears relatively thin on the radiographs, with only few eggs becoming more prominently calcified prior to oviposition.
{"title":"Oviducal Period and Egg Shell Calcification in the South African Tortoise Chersina angulata","authors":"M. Hofmeyr, G. Kuchling","doi":"10.2744/CCB-1568.1","DOIUrl":"https://doi.org/10.2744/CCB-1568.1","url":null,"abstract":"Abstract. Chersina angulata egg retention times differ among sequentially ovulated eggs from February to November, being shorter in eggs ovulated in October and November than in eggs ovulated in February, April, May, and July. More time is required to achieve eggshell calcification from July to October than from March to June. In most instances (71%) females lay their eggs when the eggshell still appears relatively thin on the radiographs, with only few eggs becoming more prominently calcified prior to oviposition.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114403957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Robust morphological data are key to systematic and ecomorphological studies, but Karoo dwarf tortoises (Chersobius boulengeri) are difficult to sample due to scarcity and secretive behavior, resulting in scant published recordings of shell dimensions based on data gathered at many locations over many years. We sampled, for the first time, a single population of Karoo dwarf tortoises in 2018–2020 and report shell dimensions for 52 males, 37 females, and 5 juveniles. Male and female shells were dimorphic in size, volume, and shape, and a comparison with speckled dwarf tortoises (Chersobius signatus) suggests subtle congeneric differences in sexual dimorphism.
{"title":"Shell Dimensions in a Population of Karoo Dwarf Tortoises, Chersobius boulengeri","authors":"V. Loehr, T. Keswick","doi":"10.2744/CCB-1564.1","DOIUrl":"https://doi.org/10.2744/CCB-1564.1","url":null,"abstract":"Abstract. Robust morphological data are key to systematic and ecomorphological studies, but Karoo dwarf tortoises (Chersobius boulengeri) are difficult to sample due to scarcity and secretive behavior, resulting in scant published recordings of shell dimensions based on data gathered at many locations over many years. We sampled, for the first time, a single population of Karoo dwarf tortoises in 2018–2020 and report shell dimensions for 52 males, 37 females, and 5 juveniles. Male and female shells were dimorphic in size, volume, and shape, and a comparison with speckled dwarf tortoises (Chersobius signatus) suggests subtle congeneric differences in sexual dimorphism.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"120 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133635069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Astrid Dedieu, Nicola Scherzer, Thomas Paumann, A.G.J. Morshed, A. Weissenbacher, Christian Walzer, D. Preininger
Abstract. Camera traps are very useful tools in determining the presence/absence of rare and cryptic species while shedding light on behavioral traits. Passive infrared triggered cameras are routinely used in homeothermic animals, but in ectothermic reptiles, this surveillance method has proven highly unreliable. As part of the conservation goal to provide better understanding and protection for the critically endangered freshwater turtle Batagur baska, we investigated their largely unknown nesting behavior and tested video-based motion detection by comparing 2 different camera-trapping systems and their settings under controlled conditions at the Vienna Zoo. A pixel-based video surveillance camera was superior to a camera trap with motion sensor. The surveillance camera allowed reliable motion detection at sensitive settings, and video capture precision could be enhanced by marking the terrapin with reflective tape. This video surveillance camera was then deployed over 2 breeding seasons (2019 and 2020) in the conservation breeding project of the northern river terrapin (B. baska, Gray 1830) in Bhawal National Park in Bangladesh. Analysis of video recording demonstrated for the first time that female northern river terrapins nested on average for a period of 1.5 hrs and produced a single clutch per year. Results indicate that females inspect sandbanks and visit suitable nesting sites several times before egg deposition, suggesting that nest-site selection is not random in B. baska. In addition, water temperature measurements of the breeding ponds in 2 captive breeding sites of the B. baska project showed an annual average temperature decrease to 168C–188C during the mating season and an average increase to 288C–318C before the nesting season. Temperatures on nesting nights vary between the 2 breeding sites and differ between nesting events within each site, suggesting that overall seasonal temperature shifts initiate the nesting periods, while other physiological and environmental factors might trigger the actual nesting event. With the help of consistent motion-triggered video recording, our study provides a first underpinning of the nesting ecology of B. baska.
{"title":"Camera Traps Provide First Insights into the Nesting Behavior of the Critically Endangered Northern River Terrapin (Batagur baska)","authors":"Astrid Dedieu, Nicola Scherzer, Thomas Paumann, A.G.J. Morshed, A. Weissenbacher, Christian Walzer, D. Preininger","doi":"10.2744/CCB-1543.1","DOIUrl":"https://doi.org/10.2744/CCB-1543.1","url":null,"abstract":"Abstract. Camera traps are very useful tools in determining the presence/absence of rare and cryptic species while shedding light on behavioral traits. Passive infrared triggered cameras are routinely used in homeothermic animals, but in ectothermic reptiles, this surveillance method has proven highly unreliable. As part of the conservation goal to provide better understanding and protection for the critically endangered freshwater turtle Batagur baska, we investigated their largely unknown nesting behavior and tested video-based motion detection by comparing 2 different camera-trapping systems and their settings under controlled conditions at the Vienna Zoo. A pixel-based video surveillance camera was superior to a camera trap with motion sensor. The surveillance camera allowed reliable motion detection at sensitive settings, and video capture precision could be enhanced by marking the terrapin with reflective tape. This video surveillance camera was then deployed over 2 breeding seasons (2019 and 2020) in the conservation breeding project of the northern river terrapin (B. baska, Gray 1830) in Bhawal National Park in Bangladesh. Analysis of video recording demonstrated for the first time that female northern river terrapins nested on average for a period of 1.5 hrs and produced a single clutch per year. Results indicate that females inspect sandbanks and visit suitable nesting sites several times before egg deposition, suggesting that nest-site selection is not random in B. baska. In addition, water temperature measurements of the breeding ponds in 2 captive breeding sites of the B. baska project showed an annual average temperature decrease to 168C–188C during the mating season and an average increase to 288C–318C before the nesting season. Temperatures on nesting nights vary between the 2 breeding sites and differ between nesting events within each site, suggesting that overall seasonal temperature shifts initiate the nesting periods, while other physiological and environmental factors might trigger the actual nesting event. With the help of consistent motion-triggered video recording, our study provides a first underpinning of the nesting ecology of B. baska.","PeriodicalId":126915,"journal":{"name":"Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121750732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：