Artificial nesting habitats as a conservation strategy for turtle populations experiencing global change

Diamondback terrapins(Malaclemys terrapin)inhabit estuaries in eastern USA and may tolerate salinity of seawater for short durations.Many North American estuaries are adversely affected by anthropogenic impacts,such as pollution,dredging and invasion by non-native plants.Many nesting areas have been altered or destroyed,causing terrapins to nest on roadsides and artificial islands made of dredged substrate from bottom sediments.Shading by non-native plants may suppress development and reduce survival of embryos.In Barnegat Bay,New Jersey,USA,there is a mosaic of natural and degraded terrapin nesting habitats.We investigated the effects of dredge soil and shade on the hatching success of diamondback terrapins to determine whether nesting habitat could be increased by using dredged bottom sediments.In year 1,unshaded nests in natural loamy-sand had the highest hatching success(55.2%),while nests in dredge soil produced no hatchlings.In year 2,nests in unshaded loamy-sand had a hatching success of 85.3%,whereas those in dredge soil,aged 1 year,had a hatching success of 59.4%.Dredge soil improved as an incubation substrate after aging 1 year by the washout of salt.Nest temperatures were generally cool and produced mostly male hatchlings.Uncontaminated dredge soil may provide suitable nesting substrates for diamondback terrapins if used after one year,and may be particularly beneficial if used for constructing islands that provide new nesting sites with reduced access of mammalian predators.

Effects of disturbance on small mammal community structure in the New Jersey Pinelands, USA

We compared small mammal community composition among undisturbed habitats and habitats disturbed by military operations on Warren Grove Gunnery Range(WGR)in the New Jersey Pinelands.WGR is one of the largest tracts of protected land within this globally rare ecosystem.Disturbance in the form of fire,mowing,soil disruption and logging has had a large effect on small mammal occurrence and distribution.Of the 14 small mammal species that occur in the Pinelands,9 live on WGR,including large populations of the southern bog lemming(Synaptomys cooperi Baird,1858)and meadow jumping mouse[Zapus hudsonius(Zimmermann,1780)].Simpson’s Index of Diversity was 0 for most disturbed sites and was generally greater in wetlands than in uplands.White-footed mouse[Peromyscus leucopus(Rafinesque,1818)]was the most common species on WGR and had a dominant effect on species diversity and community similarity indices.It dominated upland habitats and was the only species to occur in several disturbed habitats,whereas all 9 species occurred in wetlands.Principal components analysis indicated that most variation in species diversity was explained by disturbance and differences between upland and wetland habitats,due to presence of white-footed mice in disturbed and upland sites.Meadow jumping mice,southern bog lemmings and red-back voles[Myodes gapperi(Vigors,1830)]were positively correlated with wetland habitats,and pine voles[Microtus pinetorum(Le Conte,1830)],short-tail shrews[Blarina brevicauda(Say,1823)]and eastern chipmunks[Tamias striatus(Linnaeus,1758)]were associated with uplands.Habitat heterogeneity at WGR,including extensive undisturbed wetlands and uplands supported a rich diversity of small mammal species.

Mojave desert tortoise(Gopherus agassizii)thermal ecology and reproductive success along a rainfall cline

Desert resource environments(e.g.microclimates,food)are tied to limited,highly localized rainfall regimes which generate microgeographic variation in the life histories of inhabitants.Typically,enhanced growth rates,reproduction and survivorship are observed in response to increased resource availability in a variety of desert plants and short-lived animals.We examined the thermal ecology and reproduction of US federally threatened Mojave desert tortoises(Gopherus agassizii),long-lived and large-bodied ectotherms,at opposite ends of a 250-m elevation-related rainfall cline within Ivanpah Valley in the eastern Mojave Desert,California,USA.Biophysical operative environments in both the upper-elevation,“Cima,”and the lower-elevation,“Pumphouse,”plots corresponded with daily and seasonal patterns of incident solar radiation.Cima received 22%more rainfall and contained greater perennial vegetative cover,which conferred 5°C-cooler daytime shaded temperatures.In a monitored average rainfall year,Cima tortoises had longer potential activity periods by up to several hours and greater ephemeral forage.Enhanced resource availability in Cima was associated with larger-bodied females producing larger eggs,while still producing the same number of eggs as Pumphouse females.However,reproductive success was lower in Cima because 90%of eggs were depredated versus 11%in Pumphouse,indicating that predatory interactions produced counter-gradient variation in reproductive success across the rainfall cline.Land-use impacts on deserts(e.g.solar energy generation)are increasing rapidly,and conservation strategies designed to protect and recover threatened desert inhabitants,such as desert tortoises,should incorporate these strong ecosystem-level responses to regional resource variation in assessments of habitat for prospective development and mitigation efforts.