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Florida is home to several introduced animal species, especially in the southern portion of the state. Most introduced species are restricted to the urban and suburban areas along the coasts, but some species, like the Cuban Treefrog (Osteopilus septentrionalis), are locally abundant in natural protected areas. Although Cuban Treefrogs are known predators of native treefrog species as both adults and larvae, no study has demonstrated a negative effect of Cuban Treefrogs on native treefrog survival, abundance, or occupancy rate. We monitored survival, capture probability, abundance, and proportion of sites occupied by Cuban Treefrogs and two native species, Green Treefrogs (Hyla cinerea) and Squirrel Treefrogs (Hyla squirella), at four sites in Everglades National Park in southern Florida with the use of capture–mark–recapture techniques. After at least 5 mo of monitoring all species at each site we began removing every Cuban Treefrog captured. We continued to estimate survival, abundance, and occupancy rates of native treefrogs for 1 yr after the commencement of Cuban Treefrog removal. Mark–recapture models that included the effect of Cuban Treefrog removal on native treefrog survival did not have considerable Akaike's Information Criterion (AIC) weight, although capture rates of native species were generally very low prior to Cuban Treefrog removal. Estimated abundance of native treefrogs did increase after commencement of Cuban Treefrog removal, but also varied with the season of the year. The best models of native treefrog occupancy included a Cuban Treefrog removal effect at sites with high initial densities of Cuban Treefrogs. This study demonstrates that an introduced predator can have population-level effects on similar native species.
Pathogen transfer may be an important but poorly understood cost of cannibalism. Does the consumption of smaller conspecifics by Cane Toads (Rhinella marina) result in transfer of viability-reducing parasites such as nematode lungworms (Rhabdias pseudosphaerocephala)? Our experimental trials confirm that cannibalistic toads can indeed become infected, and our results are probably the first evidence of macroparasite transmission via intraspecific predation in amphibians. Our results also show that parasites acquired via cannibalism are viable, develop into fertile adults, and reduce the locomotor performance of the hosts. How cannibalism contributes to nematode transmission and spread in natural populations is not known, but we propose a scenario in which this interaction would be likely to increase the lungworm prevalence, intensity, or persistence.
Males of Tornier's Forest Toad, Nectophrynoides tornieri, were observed to perform a peculiar display posture, the ‘push-up’: the males raised themselves from a substrate (always a plant structure) by first stretching their fore legs into a ‘sit-up’ and then their hind legs to assume the position. We examined possible functions for the push-up position in manipulative behavioral experiments. In a majority of the tested males, the introduction of a conspecific male only evoked the less conspicuous sit-up display, whereas a playback of male vocalization more often triggered the full push-up position, usually followed by a vocal response. We found no association between the sit-up and the push-up display and the presence of a female N. tornieri near a male's calling perch. Our findings support the hypothesis that the push-up posture is a display in response to other calling males; whilst being the usual calling posture, it might also be important in visual communication. We describe in detail the characteristics of the call for the first time; vocalizing males were found at more elevated positions than previously reported and there were no common distinctive microhabitat features between calling sites.
Few studies have examined the spatial ecology of the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis). We used radiotelemetry to examine the seasonal home range, movement patterns, and habitat use of 21 individuals within the Blue River drainage of southern Indiana, USA. Individuals were located up to three times weekly from July 2008 through October 2009. Mean 100% minimum convex polygon (MCP) home-range sizes were much larger than previously reported and largest during the summer. Male MCPs were significantly larger than those of females. Mean linear home-range sizes were also significantly longer in the summer, but did not differ between the sexes. Hellbenders moved very little throughout the year (X¯ = 14.1 movements per individual) and over relatively short distances (X¯ = 27.5 m) to nearby shelter rocks. Most Hellbenders were routinely located under large, flat shelter rocks; however, five individuals periodically used bedrock, downed trees, and submerged tree root masses along the riverbank. Habitat use of Hellbenders was similar to that found in other studies, with 79.5% of our locations found on a gravel substrate. Our results provide essential information about a declining, low-density population of Hellbenders in need of management.
Dietary separation is an important means of differentiating ecological niches and avoiding interspecific competition between sympatric species. Congeneric species that overlap in geographic distribution provide an excellent opportunity to explore the mechanisms of coexistence. Two monitor lizards, Varanus gouldii and V. rosenbergi (Varanidae), are sympatric at a local scale in the northern Jarrah Forest of Western Australia. Both species are wide-ranging terrestrial predators of a similar size and may differentiate their ecological niche by utilizing alternative foraging strategies resulting in dietary separation. Because varanid lizards are an important group of terrestrial high-order predators in the Old World, any such separation may have important implications for faunal community structure. In total, 169 scat and stomach samples were analyzed revealing extensive dietary overlap between the species. Dietary intake was not distinguishable between species or related to individual body size. Invertebrates were most important in terms of frequency and volume, although reptiles, mammals and birds were also commonly identified. Dietary partitioning is not the mechanism allowing these congeneric varanid lizards to coexist.
With the historical and continued fragmentation of Longleaf Pine (Pinus palustris) forests, an increasing need emerges to identify remaining Black Pine Snake, Pituophis melanoleucus lodingi, populations and understand species–environment correlations so that conservation efforts for this taxon are properly directed and appropriate. This study had three main objectives: (1) to use radiotelemetry data in conjunction with GIS modeling to assess multiple scale resource selection for P. m. lodingi; (2) to use occurrence data to validate our habitat suitability model; and (3) to quantify microhabitat characteristics of P. m. lodingi locality records and evaluate differences in land cover between historical and recent records. At the landscape scale, P. m. lodingi selected evergreen forests in upland areas lacking cultivated crops, pasture and hay fields, developed areas, and roads. Within home ranges, P. m. lodingi were found closer to scrub/shrub habitat and open areas than expected. Our Boolean model reduced the area deemed suitable for P. m. lodingi by 84.3%, while accurately categorizing 75% of recent P. m. lodingi occurrences, demonstrating the potential for robust model development despite small sample sizes. We found significant habitat differences between recent and historical P. m. lodingi locality records, which corroborated the findings of our Boolean model. Recent sites of occurrence were, on average, 597 m from areas with a model score of “optimal,” whereas sites with no recent records were, on average, 1582 m from areas with an optimal score. Recent sites were characterized by significantly less canopy cover, less basal area, less midstory cover, greater percentages of grass, bare soil, and forbs in the ground cover, less shrubs and litter in the ground cover, and a more recent burn history than sites with no recent records. Areas containing historical P. m. lodingi populations are simultaneously becoming unsuitable at both the landscape and microhabitat scales. Our Boolean modeling approach represents a cost-effective way to plan for informed management actions for snake taxa of conservation concern.
The Eastern Massasauga rattlesnake, Sistrurus catenatus catenatus, is a candidate for US federal listing and is legally protected in every state or province in which it occurs. Habitat degradation and human persecution have contributed to range-wide population declines. Survival estimates are essential for a thorough understanding of population dynamics, yet are rarely reported for S. c. catenatus in the peer-reviewed literature. There has been little research on massasauga survival in managed areas of Michigan, USA, the state considered to be the last S. c. catenatus stronghold. Our objectives were to estimate survival of massasaugas during the active season (May–October) in southwestern Lower Michigan and describe causes of mortality. We captured (mid-May to late August), radiomarked, and monitored 27 adult massasaugas in 2008 and 2009 and pooled data for analyses. We observed snakes throughout the active season and estimated survival (Mayfield method) for that period (11 May–29 October; 168 d). Cause-specific mortality was investigated qualitatively. Estimated survival probability for the active season was 0.9472 (CI = 0.8518–1.0000), higher than any estimate for similar studies of which we are aware. The single mortality event observed was caused by predation. We suggest that the high massasauga survivorship in this area might be attributable to habitat management for S. c. catenatus combined with a relative lack of infrastructure and human persecution. Our results suggest that adult S. c. catenatus survival is potentially geographically variable and can be high in areas not well-investigated, such as southwestern Lower Michigan. More research would yield long-term survival trends for the studied population as well as throughout their range.
Mortality of juvenile (<122 cm total length; TL) American Alligators (Alligator mississippiensis) attributed to cannibalism on Orange Lake, Florida was examined. Alligator web tags used in mark–recapture studies were found in 12% of 267 stomachs sampled from alligators ≥168 cm TL. Captive alligators retained 76% of force-fed tags during a 588-d tag-retention trial. Models relating the probability of tag recovery to the annual probabilities of juvenile survival, cannibalism, tag retention, adult survival, and adult harvest suggested that cannibalism may on average remove 6–7% of the juvenile alligator population annually. Vulnerability continued to 140 cm TL (age 6–8 yr). Cannibalism of juveniles may serve to regulate the alligator population on Orange Lake. Alligator cannibalism may vary widely among populations, depending on demography and environmental conditions. The role and importance of cannibalism in alligator population dynamics should be more fully assessed and environmental and population factors that influence cannibalism identified to better evaluate management programs.
Herein we describe a new species of the gekkonid genus Cyrtopodion from Dadun, a town between Toksun County and Turpan City, Xinjiang Uygur Autonomous Region, Western China. It differs from congeners in China and adjacent countries by the combination of nostril bordered by rostral, first supralabial, one supranasal, and two subequal postnasals; dorsal tubercles arranged in regular longitudinal rows; 23–26 ventral scales across mid-abdomen; 97–108 scales along the ventrum of body from postmental to cloaca; 18–22 subdigital lamella beneath fourth toe; 8–10 precloacal pores in males; caudal tubercles broadly in contact laterally with each other; a single row of transversally enlarged subcaudals; dorsal bands in waving shape, much thinner than interspaces.
The taxonomic status of Typhlops lumbricalis is discussed. Populations of Typhlops lumbricalis (sensu stricto) are redescribed and restricted to the Bahamas islands. Two new Cuban species associated with T. lumbricalis are described. The new species are medium in size; rostral in dorsal view is a narrow to broad oval, preocular contacting third supralabial only, low middorsal scale count (<300), 20 scale rows anteriorly and reducing to 18 posteriorly at around midbody. These can be placed within the T. lumbricalis species group and a key to the West Indian species is presented.
La situación taxonómica del nombre Typhlops lumbricalis es discutida. Las poblaciones de Typhlops lumbricalis (sensu stricto) son redescritas y restringidas a las Bahamas. Dos nuevas especies cubanas asociadas con T. lumbricalis son descritas. Las nuevas especies son de mediano tamaño, con rostral en vista dorsal desde estrecha a oval amplia, preocular contactando solamente con la tercera supralabial, bajo conteo de escamas mediodorsales (< 300), 20 hileras de escamas anteriormente, reduciendo a 18 posteriormente alrededor del medio del cuerpo. Estas especies pueden ubicarse dentro del grupo de especies de T. lumbricalis y una clave para las especies antillanas y Bahamas es presentada.
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