Habitat Loss and Local Extinction: Linking Population Declines of Eastern Collared Lizards (Crotaphytus collaris) to Habitat Degradation in Ozark Glades

2018 ◽  
Vol 52 (3) ◽  
pp. 352-360 ◽  
Author(s):  
Casey L. Brewster ◽  
Steven J. Beaupre ◽  
John D. Willson
Keyword(s):  
Habitat Loss ◽  
Habitat Degradation ◽  
Local Extinction ◽  
Population Declines ◽  
Crotaphytus Collaris ◽  
Collared Lizards

scholarly journals Integrating bioenergetics and conservation biology: thermal sensitivity of digestive performance in Eastern Collared Lizards (Crotaphytus collaris) may affect population persistence

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Casey L Brewster ◽  
Jason Ortega ◽  
Steven J Beaupre
Keyword(s):  
Thermal Sensitivity ◽  
Metabolizable Energy ◽  
Effect Of Temperature ◽  
Valuable Insight ◽  
Feeding Rates ◽  
Crotaphytus Collaris ◽  
Reduced Body ◽  
Heat Loads ◽  
Passage Times ◽  
Collared Lizards

Abstract Information on bioenergetics can provide valuable insight into the ecology, life history and population dynamics of organisms. For ectothermic animals, thermal sensitivity of digestion is an important determinant of net assimilated energy budgets. A recent study in the Ozark Mountains indicated that eastern collared lizards (Crotaphytus collaris) restricted to encroached glades (characterized by woody vegetation encroachment) experience reduced environmental heat loads and have reduced age-specific growth and reproductive rates compared to populations in intact glades. To assess the potential impact of reduced body temperatures on assimilation rates of C. collaris in encroached glades, we conducted feeding trials across four temperature treatments (28, 31, 34 and 37°C). We tested for temperature effects on voluntary feeding rates, passage times, apparent assimilated energy (AE) and metabolizable energy (ME). Passage times decreased and voluntary feeding rates increased significantly with increasing temperature. Consumption explained the majority of variance in AE and ME, followed by the effect of temperature treatments. Using data on voluntary feeding rates, passage times and ME as a function of temperature, we estimated over a 10-fold increase in predicted daily assimilated energy across temperature treatments (28°C = 0.58 kJ/day, 31°C = 1.20 kJ/day, 34°C = 4.30 kJ/day, 37°C = 7.95 kJ/day). Thus, lower heat loads in encroached glades may cause reduced body temperature and result in restricted energy assimilation rates. Our study provides a novel approach to the integration of bioenergetics and conservation and shows the efficacy of using information on digestive performance to investigate underlying mechanisms in a conservation context.

A Multidisciplinary Investigation of the Applicability of the Pleistocene Herpetofaunal Stability Model to Collared Lizards (Crotaphytus collaris)

1999 ◽  
Vol 13 ◽  
pp. 81 ◽  
Author(s):  
Delbert W. Hutchison ◽  
Simon T. Malcomber ◽  
L. Susan Pletscher
Keyword(s):  
Crotaphytus Collaris ◽  
Stability Model ◽  
Collared Lizards

scholarly journals A population survey of the estuarine crocodile in the Ayeyarwady Delta, Myanmar

Oryx ◽  
2000 ◽  
Vol 34 (4) ◽  
pp. 317-324 ◽  
Author(s):  
John Thorbjarnarson ◽  
Steven G. Platt ◽  
U. Saw Tun Khaing
Keyword(s):  
Law Enforcement ◽  
Survey Data ◽  
Habitat Loss ◽  
Population Survey ◽  
Total Population ◽  
Population Declines ◽  
Wildlife Sanctuary ◽  
Coastal Regions ◽  
The Status ◽  
Crocodylus Porosus

AbstractThe estuarine crocodile Crocodylus porosus was formerly abundant in coastal regions of Myanmar, but is now known principally from the lower Ayeyarwady Delta. We conducted a survey during January 1999 to assess quantitatively the status of crocodile populations in protected areas of the lower delta. Spotlight counts were conducted along 275.4 km of waterways. Sixty-one crocodiles (50 juveniles, 4 subadults, 2 adults and 5 eyeshines) were observed in the Meinmahla Kyun Wildlife Sanctuary (MKWS), and the total population was estimated to be less than 100. The Kadônkani and Pyindaye Reserved Forests (RF) apparently no longer support viable populations. Although crocodiles remain critically endangered in the region, a comparison with survey data from 1980 suggests localized recovery is occurring in MKWS. Population declines are attributed to a combination of commercial skin hunting, habitat loss, drowning in fishing nets and over-collection of living animals to supply crocodile farms. A programme of law enforcement, habitat protection and head-starting juveniles is necessary to ensure the continued survival of estuarine crocodiles in the Ayeyarwady Delta.

Cryptic and cumulative impacts on the wintering habitat of the endangered black-faced spoonbill (Platalea minor) risk its long-term viability

2017 ◽  
Vol 45 (2) ◽  
pp. 147-154 ◽  
Author(s):  
EVAN J. PICKETT ◽  
MELANIE CHAN ◽  
WENDA CHENG ◽  
JOHN ALLCOCK ◽  
SIMBA CHAN ◽  
...  
Keyword(s):  
Climate Change ◽  
Habitat Loss ◽  
Population Change ◽  
Anthropogenic Impacts ◽  
Population Viability Analysis ◽  
Cumulative Impacts ◽  
Population Declines ◽  
Distribution Models ◽  
Waterbird Species

SUMMARYThe East Asian–Australasian flyway contains some of the most threatened habitats in the world, with at least 155 waterbird species reliant on the tidal habitats it comprises. The black-faced spoonbill (Platalea minor) is an iconic endangered species distributed across the coast of East Asia. Its population suffered a severe decline into the 1990s, but extensive monitoring and conservation interventions have aided a substantial recovery of the species. We used a population viability analysis based on data collected over the past two decades in conjunction with species distribution models to project spatially explicit models of population change for the next 35 years. Over nearly all scenarios of habitat loss and climate change, the global spoonbill population was projected to increase in the short-term due to low population numbers likely well below current population carrying capacities. However, climate change and habitat loss together threaten the recovery of the spoonbill population such that, by 2050, population declines are apparent as a consequence of these cumulative impacts. These threats are also cryptic and represent a challenge to the conservation of species recovering from anthropogenic impacts; observed population increases can hide large reductions in habitat suitability that threaten the long-term viability of species.

Capital energy drives production of multiple clutches whereas income energy fuels growth in female collared lizards Crotaphytus collaris

Oikos ◽  
2011 ◽  
Vol 120 (6) ◽  
pp. 915-921 ◽  
Author(s):  
Rorry S. Telemeco ◽  
Troy A. Baird
Keyword(s):  
Crotaphytus Collaris ◽  
Collared Lizards

scholarly journals Synergistic impacts of habitat loss and fragmentation on model ecosystems

2016 ◽  
Vol 283 (1839) ◽  
pp. 20161027 ◽  
Author(s):  
Lewis J. Bartlett ◽  
Tim Newbold ◽  
Drew W. Purves ◽  
Derek P. Tittensor ◽  
Michael B. J. Harfoot
Keyword(s):  
Land Use ◽  
Habitat Loss ◽  
Plant Biomass ◽  
Synergistic Effects ◽  
Ecosystem Model ◽  
Ecosystem Structure ◽  
Population Declines ◽  
Ecosystem Responses ◽  
Habitat Loss And Fragmentation ◽  
Biomass Loss

Habitat loss and fragmentation are major threats to biodiversity, yet separating their effects is challenging. We use a multi-trophic, trait-based, and spatially explicit general ecosystem model to examine the independent and synergistic effects of these processes on ecosystem structure. We manipulated habitat by removing plant biomass in varying spatial extents, intensities, and configurations. We found that emergent synergistic interactions of loss and fragmentation are major determinants of ecosystem response, including population declines and trophic pyramid shifts. Furthermore, trait-mediated interactions, such as a disproportionate sensitivity of large-sized organisms to fragmentation, produce significant effects in shaping responses. We also show that top-down regulation mitigates the effects of land use on plant biomass loss, suggesting that models lacking these interactions—including most carbon stock models—may not adequately capture land-use change impacts. Our results have important implications for understanding ecosystem responses to environmental change, and assessing the impacts of habitat fragmentation.

scholarly journals Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus)

2017 ◽  
Author(s):  
Susan J Crockford
Keyword(s):  
Sea Ice ◽  
Population Size ◽  
Habitat Loss ◽  
Polar Bear ◽  
Population Decline ◽  
Ursus Maritimus ◽  
The Arctic ◽  
Polar Bears ◽  
Population Declines ◽  
Sea Ice Decline

The polar bear (Ursus maritimus) was the first species to be classified as threatened with extinction based on predictions of future conditions rather than current status. These predictions were made using expert-opinion forecasts of population declines linked to modeled habitat loss – first by the International Union for the Conservation of Nature (IUCN)’s Red List in 2006, and then by the United States Fish and Wildlife Service (USFWS) in 2008 under the Endangered Species Act (ESA), based on data collected to 2005 and 2006, respectively. Both assessments predicted significant population declines of polar bears would result by mid-century as a consequence of summer sea ice extent rapidly reaching 3-5 mkm2 on a regular basis: the IUCN predicted a >30% decline in total population, while the USFWS predicted the global population would decline by 67% (including total extirpation of ten subpopulations within two vulnerable ecoregions). Biologists involved in these conservation assessments had to make several critical assumptions about how polar bears might be affected by future habitat loss, since sea ice conditions predicted to occur by 2050 had not occurred prior to 2006. However, summer sea ice declines have been much faster than expected: low ice levels not expected until mid-century (about 3-5 mkm2) have occurred regularly since 2007. Realization of predicted sea ice levels allows the ‘rapid sea ice decline = population decline’ assumption for polar bears to be treated as a testable hypothesis. Data collected between 2007 and 2015 reveal that polar bear numbers have not declined as predicted and no subpopulation has been extirpated. Several subpopulations expected to be at high risk of decline remained stable and five showed increases in population size. Another at-risk subpopulation was not counted but showed marked improvement in reproductive parameters and body condition with less summer ice. As a consequence, the hypothesis that repeated summer sea ice levels of below 5 mkm2 will cause significant population declines in polar bears is rejected, a result that indicates the ESA and IUCN judgments to list polar bears as threatened based on future risks of habitat loss were scientifically unfounded and that similar predictions for Arctic seals and walrus may be likewise flawed. The lack of a demonstrable ‘rapid sea ice decline = population decline’ relationship for polar bears also potentially invalidates updated survival model outputs that predict catastrophic population declines should the Arctic become ice-free in summer.

scholarly journals Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus)

2017 ◽  
Author(s):  
Susan J Crockford
Keyword(s):  
Sea Ice ◽  
Population Size ◽  
Habitat Loss ◽  
Polar Bear ◽  
Population Decline ◽  
Ursus Maritimus ◽  
The Arctic ◽  
Polar Bears ◽  
Population Declines ◽  
Sea Ice Decline

The polar bear (Ursus maritimus) was the first species to be classified as threatened with extinction based on predictions of future conditions rather than current status. These predictions were made using expert-opinion forecasts of population declines linked to modeled habitat loss – first by the International Union for the Conservation of Nature (IUCN)’s Red List in 2006, and then by the United States Fish and Wildlife Service (USFWS) in 2008 under the Endangered Species Act (ESA), based on data collected to 2005 and 2006, respectively. Both assessments predicted significant population declines of polar bears would result by mid-century as a consequence of summer sea ice extent rapidly reaching 3-5 mkm2 on a regular basis: the IUCN predicted a >30% decline in total population, while the USFWS predicted the global population would decline by 67% (including total extirpation of ten subpopulations within two vulnerable ecoregions). Biologists involved in these conservation assessments had to make several critical assumptions about how polar bears might be affected by future habitat loss, since sea ice conditions predicted to occur by 2050 had not occurred prior to 2006. However, summer sea ice declines have been much faster than expected: low ice levels not expected until mid-century (about 3-5 mkm2) have occurred regularly since 2007. Realization of predicted sea ice levels allows the ‘rapid sea ice decline = population decline’ assumption for polar bears to be treated as a testable hypothesis. Data collected between 2007 and 2015 reveal that polar bear numbers have not declined as predicted and no subpopulation has been extirpated. Several subpopulations expected to be at high risk of decline remained stable and five showed increases in population size. Another at-risk subpopulation was not counted but showed marked improvement in reproductive parameters and body condition with less summer ice. As a consequence, the hypothesis that repeated summer sea ice levels of below 5 mkm2 will cause significant population declines in polar bears is rejected, a result that indicates the ESA and IUCN judgments to list polar bears as threatened based on future risks of habitat loss were scientifically unfounded and that similar predictions for Arctic seals and walrus may be likewise flawed. The lack of a demonstrable ‘rapid sea ice decline = population decline’ relationship for polar bears also potentially invalidates updated survival model outputs that predict catastrophic population declines should the Arctic become ice-free in summer.

Population genetics in a fragmented population of the European tree frog (Hyla arborea)

2013 ◽  
Vol 34 (1) ◽  
pp. 95-107 ◽  
Author(s):  
Astrid Krug ◽  
Heike Pröhl
Keyword(s):  
Gene Flow ◽  
Habitat Fragmentation ◽  
Habitat Degradation ◽  
Isolation By Distance ◽  
Sampling Site ◽  
Source Population ◽  
Tree Frog ◽  
Population Declines ◽  
Hyla Arborea ◽  
Genetic Clusters

Habitat degradation and fragmentation are known to be major threats for population persistence in European amphibians. The European tree frog Hyla arborea has suffered from dramatic population declines in the last decades and has therefore been categorised as threatened in many Red Data lists. In the region of Hannover (Germany), the European tree frog has a fragmented distribution. The aim of our study was to infer the genetic consequences of habitat fragmentation in this area by examining genetic variation and population structure. DNA samples from 193 individuals from 11 sampling sites (10 sampling sites located 2 to 32 km apart from each other near Hannover and for comparison one sampling site 140 km northeast) were analysed with eight highly polymorphic microsatellite loci. Bayesian analyses indicated that the tree frog occurrences near Hannover were fragmented into four genetically distinct clusters according to their geographical distribution. Pairwise genetic distances between sampling sites varied between 0 and 0.23 (FST) and 0 and 0.48 (Dest) and indicated high to moderate gene flow within genetic clusters and nearly absent gene flow among genetic clusters. Moreover, we identified a potential source population within the region for an introduced population in the southwest of Hannover. Our data suggest that the genetic structure is influenced in part by isolation by distance and in part by lack of habitat or migration barriers. Habitat fragmentation should by counteracted by targeted conservation measures in areas where gaps in distribution and genetic fragmentation have been revealed.

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