Kristopher B. Karsten

Do Panther Chameleons Bask to Regulate Endogenous Vitamin D3 Production

Basking by ectothermic vertebrates is thought to have evolved for thermoregulation. However, another beneficial effect of sunlight exposure, specifically the ultraviolet B (UV‐B) component, includes endogenous production of vitamin D3. In the laboratory, panther chameleons exhibited a positive phototaxis to greater visible, ultraviolet A (UV‐A) and UV‐B light. However, with equivalent high irradiances of UV‐A or UV‐B, their response to UV‐B was significantly greater than it was to UV‐A. Exposure of in vitro skin patches of panther chameleons to high UV‐B (90 μW/cm2) for 1 h significantly enhanced vitamin D3 concentration. Voluntary exposure to higher UV‐B irradiance (70 vs. 1 μW/cm2) resulted in greater circulating 25‐hydroxyvitamin D3 in female panther chameleons (604 vs. 92 ng/mL). Depending on dietary intake of vitamin D3, chameleons adjusted their exposure time to UV‐B irradiation as if regulating their endogenous production of this vital hormone. When dietary intake was low (1–3 IU/g), they exposed themselves to significantly more UV‐producing light; when intake was high (9–129 IU/g), they exposed themselves to less. Vitamin D3 photoregulation seems to be an important additional component of the function of basking.

A unique life history among tetrapods: An annual chameleon living mostly as an egg

The ≈28,300 species of tetrapods (four-limbed vertebrates) almost exclusively have perennial life spans. Here, we report the discovery of a remarkable annual tetrapod from the arid southwest of Madagascar: the chameleon Furcifer labordi, with a posthatching life span of just 4–5 months. At the start of the active season (November), an age cohort of hatchlings emerges; larger juveniles or adults are not present. These hatchlings grow rapidly, reach sexual maturity in less than 2 months, and reproduce in January–February. After reproduction, senescence appears, and the active season concludes with population-wide adult death. Consequently, during the dry season, the entire population is represented by developing eggs that incubate for 8–9 months before synchronously hatching at the onset of the following rainy season. Remarkably, this chameleon spends more of its short annual life cycle inside the egg than outside of it. Our review of tetrapod longevity (>1,700 species) finds no others with such a short life span. These findings suggest that the notorious rapid death of chameleons in captivity may, for some species, actually represent the natural adult life span. Consequently, a new appraisal may be warranted concerning the viability of chameleon breeding programs, which could have special significance for species of conservation concern. Additionally, because F. labordi is closely related to other perennial species, this chameleon group may prove also to be especially well suited for comparative studies that focus on life history evolution and the ecological, genetic, and/or hormonal determinants of aging, longevity, and senescence.

Ultraviolet Exposure and Vitamin D Synthesis in a Sun‐Dwelling and a Shade‐Dwelling Species of Anolis: Are There Adaptations for Lower Ultraviolet B and Dietary Vitamin D3 Availability in the Shade?

We compared the natural ultraviolet B (UV‐B) exposure, dietary vitamin D, and skin‐generated vitamin D synthesis for adult males of two species of Jamaican anoles. The more shade‐tolerant and thermal‐conforming Anolis lineotopus merope, rarely exposed to full sun, experienced less UV‐B irradiation in its shady environment than the more heliophilic and thermophilic Anolis sagrei, which frequently basked in full sun during the morning hours (0800–1100 hours). Both species obtained detectable levels of vitamin D3 in their diet, but the heliophilic A. sagrei obtained more. To compensate for less availability of UV‐B and dietary vitamin D, the skin of A. lineotopus merope seems to have acquired a greater sensitivity than that of A. sagrei regarding UV‐B‐induced vitamin D3 photobiosynthesis. We assessed this by observing a greater conversion of provitamin D to photoproducts in skin exposed to UV‐B from a sunlamp. The reduced skin sensitivity of A. sagrei regarding vitamin D photobiosynthesis may reflect a correlated response associated with less need for vitamin D photobiosynthesis and greater need for UV‐B screening capacity as an adaptation to a more damaging UV‐B environment. However, the possibility that adaptations for photobiosynthesis of vitamin D and for protection from skin damage could involve independent mechanisms needs investigation. Also, the ability to behaviorally regulate UV‐B exposure, as shown for the panther chameleon, would benefit both species of Anolis and should be investigated.

Panther chameleons, Furcifer pardalis, behaviorally regulate optimal exposure to UV depending on dietary vitamin D3 status.

Reptiles may bask for reasons other than thermoregulation. One alternative is to regulate homeostasis of vitamin D3, a hormone essential to the health of many reptiles. Maintenance of vitamin D3 homeostasis requires either regulation of exposure to ultraviolet radiation (UV) or ingested vitamin D3. However, the prey items of most vertebrates tend to be low in vitamin D3. Thus, basking may be the primary opportunity for vitamin D3 regulation. We tested the hypothesis that panther chameleons (Furcifer pardalis) behaviorally regulate exposure to UV in natural sunlight with high precision, accuracy, and effectiveness. Panther chameleons with low dietary vitamin D3 intake significantly increased exposure to UV in natural sunlight compared to those with high dietary vitamin D3 intake. All lizards fed low dietary vitamin D3 regulated within optimal UV levels with extreme effectiveness (ability to regulate within optimal UV levels relative to available UV). Chameleons of both dietary treatments regulated UV exposure with great precision, exhibiting little variation among individuals within treatments. Our results add to a growing body of literature that empirically demonstrates the importance of basking for nonthermoregulatory purposes and, more specifically, as an integral mechanism for the regulation of a vital hormone, vitamin D3.

Social Behavior of Two Species of Chameleons in Madagascar: Insights Into Sexual Selection

Abstract Signaling plays a critical role in social behavior, particularly in polygynous systems where males compete with rival males and use signals to attract mates. We quantified visual signals and social behavior in two previously unstudied species of chameleons in Madagascar, Furcifer labordi and F. verrucosus. Females of both species displayed distinct color patterns that signaled either nonreceptivity or potential sexual receptivity. Nonreceptive females rejected all male courtship. Potentially receptive F. verrucosus females mainly allowed males to attempt copulation, whereas potentially receptive F. labordi females were selective. We found that the fleshy, paddle-like rostral appendage in F. labordi was used only during courtship, whereas other studies showed that hard, keratinized appendages were used for male combat. During male-male contests, F. labordi had much more physically intense encounters, possibly to assess opponent quality more accurately since adult male F. labordi were significantly more size-matched than adult male F. verrucosus. Our study elucidated the role of social signals in these species, illustrated the atypical social behavior of chameleons compared to other lizards, and provided testable hypotheses to further delineate sexual selection in this understudied group. Sexual selection, especially intersexual selection, appears more likely in F. labordi than in F. verrucosus.

Wind Turbines do not Negatively Affect Nest Success in the Dickcissel (Spiza americana)

ABSTRACT. Proliferation of wind energy across the Great Plains of the United States has the potential to negatively affect many grassland birds through displacement, avoidance, or changes in nesting ecology. This is troublesome because grassland birds have had the highest average annual rate of decline over the past several decades. We studied the potential indirect effects of wind turbines on nesting success in Dickcissels (Spiza americana) at a utility-scale wind farm in north-central Texas in 2010 and 2011. We monitored 195 nests and found that proximity to a wind turbine did not affect nest density or nest-site characteristics. We used an information-theoretic approach with logistic exposure modeling to identify the most likely models of nest fate. Nest initiation day and distance to wind turbine were the most important predictors of nest success. Proximity to a wind turbine did not reduce nest success. Furthermore, the daily survival rates at our site were within the range documented for Dickcissels at other sites without wind-energy developments. For the monitored nests, snake predation was the greatest source of nest failure and depredated nests were closer to woodland edges than to wind turbines. This may be because wind turbines were farther away from wooded edges. On the other hand, we cannot rule out the possibility that wind-energy development influenced predator behavior and activity, and this may warrant additional investigation. We recommend further research into the breeding ecology of a diverse selection of grassland species to fully assess the indirect effects of wind-energy development on grassland birds.

NESTING SUCCESS OF SCISSOR-TAILED FLYCATCHERS (TYRANNUS FORFICATUS) AT A WIND FARM IN NORTHERN TEXAS

Abstract We investigated indirect effects of wind turbines on nesting success of scissor-tailed flycatchers (Tyrannus forficatus). We tracked the fate of 32 nests at Wolf Ridge Wind, LLC, Cooke County, Texas, during the breeding season in 2009. Overall rates of predation on nests were high, reproductive success was low, daily rates of survival were only 93.5%, only 16% of nests fledged ≥1 offspring, and nests had only a 13.3% chance of survival from initiation to fledging. Amount of canopy cover and distance to nearest turbine best predicted success or failure of nests; nests with less canopy cover that were closer to a wind turbine had a higher daily rate of survival than nests with more canopy cover farther away. Less canopy cover might be associated with fewer terrestrial or arboreal predators on nests, while proximity to turbines might reduce aerial predation on nests. Resumen Investigamos los efectos indirectos de las turbinas de viento en el éxito reproductivo del papamoscas tijereta (Tyrannus forficatus). Rastreamos los fines de 32 nidos en Wolf Ridge Wind, LLC, condado de Cooke, Texas, durante la temporada reproductiva del 2009. Las tasas de depredación de nidos en general fueron altas y el éxito reproductivo fue bajo, con las tasas de sobrevivencia por día de sólo 93.5%, sólo 16% de los nidos produjeron ≥1 crías, y los nidos tuvieron una oportunidad de sobrevivir desde el inicio del nido hasta la salida de los volantones de sólo 13.3%. La cantidad de la cobertura del dosel y la distancia a la turbina más próxima predijeron mejor el éxito o el fracaso del nido; nidos con menos cobertura del dosel y más cerca a la turbina más próxima tuvieron una tasa de sobrevivencia por día más alta que los que construyeron más lejos y con más cobertura del dosel. Menos cobertura del dosel puede estar asociada con menos depredadores terrestres o arbóreos del nido, mientras que la proximidad a la turbina puede reducir la frecuencia de los depredadores aéreos del nido.

Effect of Wind Turbine Proximity on Nesting Success in Shrub-nesting Birds

Abstract Wind energy development is rapidly expanding globally, as are concerns about the potential threats wind facilities pose to bird and bat populations. To date, many studies have explored the direct impacts of wind turbines on wildlife, such as wildlife-turbine collisions, but few have addressed indirect impacts, such as habitat degradation. These potentially subtle impacts can have far reaching effects on the abundance, distribution, survival, and breeding success of wildlife. We conducted a study to assess whether proximity of wind turbines to shrub-nesting birds influenced rates of nest failure associated mainly with depredation and brood parasitism by Brown-headed Cowbirds (Molothrus ater). During the primary nesting period of five passerine species, we monitored 253 active nests. We used a logistic-exposure method to model nest fate as a function of the important variables identified (including distance from turbine and brood parasitism). Our results indicate little relation between nest success and distance to turbine, with one exception, the Blue-gray Gnatcatcher (Polioptila caerule). For this passerine, we found nests closer to wind turbines had a lower probability of being brood parasitized and subsequently had higher nest success rates. We recommend future studies explore the potential implications of wind energy development on brood parasites, such as the Brown-headed Cowbird. As there is regulatory and social pressure to devise management strategies that reduce the impact of brood parasites on species of concern, any opportunities to decrease the risk of brood parasitism could be of benefit.

Population densities and conservation assessments for three species of chameleons in the Toliara region of south-western Madagascar

Madagascar is a high conservation priority. Rainforests receive most of the focus, but the dry deciduous and spiny forests of south-western Madagascar house many endemics, are under high deforestation pressure, and remain largely unprotected. Charismatic vertebrates, like chameleons, face a secondary threat: harvesting for the commercial pet trade. Six chameleons inhabit the arid southwest near Toliara: Furcifer antimena, F. belalandaensis, F. labordi, F. lateralis, F. oustaleti, and F. verrucosus. We measured population densities of three of those species. Furcifer verrucosus has a large distribution, was dense (97.7 ha −1 ; 95% CI = 60.2-158.6), and inhabited forests and anthropogenic habitats. Furcifer labordi was much less dense (30.8 ha −1 ; 13.4-70.9), has a restricted range, and has a unique life history that makes it susceptible to perturbations from deforestation or illegal harvesting. Furcifer antimena was the least dense (17.0 ha −1 ; 9.3-30.9) and has an even smaller distribution range. We lack density data for F. lateralis, but this species was abundant in anthropogenic habitats. Within their respective ranges, there are currently no protected areas for F. antimena and only few for F. labordi; these two species are far less abundant than the more widely spread F. verrucosus. We recommend that high conservation priority be focused on F. antimena and the southern populations of F. labordi due to their restricted distributions, susceptibility to extirpation, lower population densities, and lack of formal protection. Establishing protected areas in the Ranobe region and north of the Fiherenana River, in the Belalanda region, would help protect important populations of these vulnerable species.

Development of tetranucleotide microsatellite loci and a non-invasive DNA sampling method for Texas horned lizards (Phrynosoma cornutum)

We developed a non-invasive DNA sampling method and 15 tetranucleotide microsatellite markers for Texas horned lizards (Phrynosoma cornutum). Swabbing the cloaca with a small cotton swab and preserving the cells in lysis buffer was an effective method to obtain tissue for DNA extraction. Loci were highly polymorphic with 8–25 alleles and observed heterozygosity was high (0.71–0.96). Some of these loci can also be used for round-tailed horned lizards (P. modestum).