Reptile Behavior and Ecology I2021-07-23 09:15 - 12:00 |
| Moderator: Gordon Rodda |
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1. 09:15 IN-PERSON Dewlap Brightness and Malaria Infection: a Test of the Hamilton-Zuk Hypothesis. Tiffany Doan*, New College of Florida tiffperu@yahoo.com
Anolis sagrei, or brown anoles, are a small invasive lizard species common throughout the Southeastern United Statesthat may become infected with the malaria parasite Plasmodium floridense.Males’ bright red dewlaps are used as a signal during territorial contests with other males and may be used to attract females.The Hamilton-Zuk hypothesis indicates that parasites may influence the appearance of sexual traits, such as a dewlap, within an infected individual,resulting in higher sexual selection for the males displaying traits that would indicate greater parasite resistance. In this study, I investigated the relationship between malarial infection and perceived dewlap brightness ofA. sagrei.I hypothesized that males infected by the parasites would have duller dewlap color, in accordance with the Hamilton-Zuk hypothesis. I tested this hypothesis by capturing male brown anoles in central and southwest Florida, taking blood samples to examine for malarial infection, and measuring the color of their dewlaps with a handheld spectrophotometer. I then quantified dewlap brightness using a formula for relative luminance and examined the blood samples microscopically using standard procedures. In contradiction to the predictions, I found that the dewlaps of infected Anolis sagreiwere significantly brighter than the dewlaps of uninfected lizards. Some previous studies on other taxa have similarly found that animals with parasitic infection display brighter secondary sexual characteristics than uninfected animals, though the mechanism remains unclear. Additional studies that take into account predation, age, and other factors will be necessary to understand why infected lizards have brighter dewlap coloration. |
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2. 09:30 IN-PERSON Why do Mothers Care? Assessing the Benefits of Female–Neonate Associations in a Viviparous Andean Lizard from the Argentine Puna. Soledad Valdecantos, Universidad Nacional de Salta; Sarah M. Wenner, California State University, Northridge; Jeanne M. Robertson, California State University, Northridge; Maxwell H. Espinoza, Valley International Preparatory High School; Carolina Lobo Terán, Unviersidad Nacional de Salta; Robert E. Espinoza*, California State University, Northridge robert.e.espinoza@csun.edu
Parental care (PC) is rare in squamates and few studies have identified the benefits selecting for this grouping behavior. We investigated this phenomenon in Liolaemus multicolor, a viviparous Andean lizard with putative PC exhibited as long-term associations between adult females and neonates. Lizards were studied at Nevado de Acay, Salta, Argentina (~4300 m) by (1) employing mark–recapture and focal-animal observations to quantify the rate and duration of female–neonate associations in nature; (2) conducting a kinship analysis based on ~500 SNPs to assess maternity among stable female–neonate groupings; and (3) introducing tethered conspecifics (neonates or adult males or females) to focal females with and without neonates to determine whether females defended associated neonates in the field. Our investigation revealed (1) females formed stable associations with 1–4 neonates for up to 4 months; (2) most (84%) female–neonate groups (n = 13) represented mother–offspring associations; (3) most (86%) field introductions led to aggressive interactions between focal females and intruders; (4) most of those fights were initiated by focal females with neonates (51%) vs. either single focal females (31%) or tethered intruders (11%); and (5) females with neonates were more aggressive towards males, whereas unassociated females never attacked males and more frequently attacked neonates. These results support our hypothesis that long-term mother–offspring associations in L. multicolor likely confer fitness advantages by improving neonate survival in the harsh environment of the Argentine Puna. Future studies will compare the long-term survival of orphaned and mother-associated neonates. |
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3. 09:45 IN-PERSON The Use of High-Frequency Accelerometry to Quantify Unseen Behaviors of Herps: A Case Study of Prairie Rattlesnakes (Crotalus viridis). Rulon Clark*, San Diego State University; Ryan Hanscom, San Diego State University; Dominic DeSantis, Georgia College & State University rclark@sdsu.edu
Many reptiles and amphibians are cryptic and secretive animals, spending large parts of their lives hidden in microhabitats that make them very difficult for humans to observe directly. Such species also tend to be sensitive to the nearby presence of human observers, further precluding direct observation as a viable technique for quantifying behavior. Although field-based surveillance equipment can be used in some instances to assemble large behavioral datasets, this technique is useful for only a limited subset of behaviors (i.e., those exhibited while the animal remains in one place), and is labor intensive. We believe a way forward in this area is the combination of limited direct field observations with high-frequency movement data logged by animal-borne accelerometers. This tool is being widely exploited by ornithologists and mammalogists, and can reveal extraordinary detail about the moment-to-moment behavior and activity of free-ranging individuals in nature. In comparison, the use of accelerometry lags behind in herpetology, despite the high potential and relatively low cost of such an approach. Miniature accelerometers that can log movement data at rates of 20 Hz or more for ~7 days are now small enough to be carried by animals as small as 20 g, making the approach suitable for a range of smaller-bodied species. Here, we provide details on our initial attempts to validate accelerometry datasets to study the feeding ecology of Prairie Rattlesnakes, including a discussion of various options for short term attachment of accelerometers to snakes. |
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5. 10:45 IN-PERSON Lizards peak in deserts, snakes are richest in the tropics; do these reflect the environments of their origins? Gordon Rodda*, USGS Fort Collins Science Center roddag@usgs.gov
Over the long run, one expects each species to adapt to its natural environment. Yet, many equatorial lizards achieve higher population densities in more open sites than the forests in which they naturally reside. Ecotones associated with natural disturbances (e.g., treefalls) provide access to two habitats and might be more attractive places to live, though this logic would apply universally. Taking the centroid of its geographic range as the location of each species, twice as many lizard species are found at latitude 19 as at the equator. Species richness increases more-or-less linearly from the equator to 19 degrees, and then decreases linearly to 50 degrees. Nineteen degrees is the latitude of the Sahara, Namib, and Australian Deserts, more open and sunny than the tropical forests. This conflicts with the generalization that species diversity is maximal at the equator, and suggests that lizards are better adapted to deserts than tropical forests. One possible reason is that two-thirds of lizard families arose prior to the advent of angiosperms, at a time when tropical forests had less canopy closure, due to limited plant growth forms (e.g., conifers, palms, cycads), and possibly heavy browsing by fast-growing and insatiable herbivorous dinosaurs. In contrast, 78% of snake families – including pythonids, colubrids, and most terrestrial species – arose after the advent of angiosperms, and therefore might be better adapted to the angiosperm-rich environments with which we are familiar today. Snake species richness declines more-or-less monotonically from the equator to 50 degrees, in keeping with general expectations. |
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6. 11:00 IN-PERSON The Use of 3D-printed Snake Models to Investigate Predation Risk. Oceane Da Cunha*, University of Texas at El Paso; Rio Dominguez, University of Texas at El Paso; L. Miles Horne, University of Texas at El Paso; Vicente Mata-Silva, University of Texas at El Paso; Jerry Johnson, University of Texas at El Paso odacunha@miners.utep.edu
Prey can respond to predation risk by morphological adaptations or by altering their behavior. These modifications are costly for individuals and appear to directly influence prey dynamics. This study aims to investigate the effects of predation risk on the spatial ecology of the Western Diamondback Rattlesnake (Crotalus atrox). To do so, a 3D-printed model was designed to accurately represent an adult and a juvenile C. atrox. Thirty of these 3D-printed models were deployed at the Indio Mountains Research Station (Hudspeth county, TX) in June 2020. Each model was coupled with a game camera to observe any potential interactions. For each model, data about the macrohabitat and microhabitat were gathered. Nine C. atrox were concurrently radio-tracked and the same habitat data were collected at each relocation. Random forest models were used to determine which ecological predictors are the most important in both the detection of 3D-printed models by predators and the visibility of C. atrox. The main predictors for model detection by predators were month, model size, and vegetation percentage. On the other hand, the main predictors of visibility of a snake were concealment source, concealment percentage, and body temperature. Further analyses are required to determine if C. atrox selects habitat to avoid predators. However, combining the use of 3D-printed models and telemetry can help gain new insights into the effects of predation pressure. |
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7. 11:15 IN-PERSON Thermal ecology of Northern Water Snakes (Nerodia sipedon) in a northern wetland in central Michigan. John Rowe*, Alma College; Tyler Goerge, Ohio University; Chelsea Martin, Loma Linda University; William Mulligan, Grand Valley State University rowe@alma.edu
We studied the thermal biology of north-temperate Northern Water Snakes (Nerodia sipedon) in central Michigan by remote radiotelemetry monitoring of snake body temperature (Tb). Our goals included evaluation of thermoregulatory capabilities at a locality that we viewed to be a spatially heterogeneous thermal environment, seasonal variations in relative investment in thermoregulation, and the effects of sex on thermoregulation. During summer, snakes showed diel Tb cycling using the open Sphagnum mat for late morning warming and shuttling among different microhabitats until early evening when a monotonic decline in Tb ensued. Snakes attained Tb within their laboratory-determined thermoregulatory set point range (Tset = 28–33 °C) mostly during late afternoon and with average percentages of Tb values for individual snakes within Tset range when permitted by operative temperatures (Ex) between 68 and 70% of the time depending on method of measurement. Relatively high investment in thermoregulation when thermal conditions were poor occurred only during September and declined as snakes prepared to overwinter. We did not detect intersexual differences in thermoregulation. Relative to a population of N. sipedon at a higher latitude in Ontario our snakes showed a relatively high Tset range and thermoregulated more effectively, particularly during the daylight hours. It remains unclear how much inter-population variation in thermoregulation is due to potential adaptations to latitude, to habitat differences, or variations in methodologies. |
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8. 11:30 IN-PERSON Exploring the Role of Long-term Dispersal in Determining the Species Richness and Trait Space of Communities of Neotropical Snakes (Dipsadidae). Juan Ramirez Ramirez*, Department of Biology, San Diego State University; Tod Reeder, Department of Biology, San Diego State University; Marko Spasojevic, Department of Evolution, Ecology, and Organismal Biology, University of California, jramirezramirez@sdsu.edu
Determining if biological communities are saturated with species (i.e., if they reached the limit of species they can harbor) is a fundamental question in ecology. A common approach for testing for saturation is to examine if the species richness of communities increases after colonization events. However, most studies using this approach are limited to small temporal scales, and few consider potential redundancies in the ecological roles of taxa. Here we explored if colonization events after the Great American Biotic Interchange (the closure of the Panamanian Isthmus) resulted in increases in the species richness of a series of communities of the snake family Dipsadidae. We identified the number and the direction of dispersal events between Central and South America by estimating ancestral areas based on a time-calibrated phylogenetic analysis. We then evaluated if the similarity on six functional traits among species inhabiting the communities of interest correlates to the number of taxa colonizing them. Our results show that communities with more colonization events did not have more species or increased functional diversity, indicating they are saturated. Our study is among the first to recover evidence of community saturation while assessing the impacts of biotic introductions across any temporal scale. Such a discrepancy supports the idea that the apparent unsaturation of modern communities is temporary, as biotic interactions can require considerable amounts of time to unfold. Further studies on other taxa and geographical settings are needed to confirm the generality of this expectation and its implications on the management of introduced species. |
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9. 11:45 VIRTUAL Spatial Use and Diel Activity Patterns in Amazon Basin Emerald Tree Boas (Corallus batesii). Elizabeth Haseltine*, Zoo Atlanta; Jadyn Sethna, Georgia Institute of Technology; Ellen Sproule, Zoo Atlanta; Savannah Berry, Georgia Institute of Technology; Marieke Gartner, Zoo Atlanta; Joseph Mendelson, Zoo Atlanta lhaseltine64@yahoo.com
Corallus batesiiis a boid snake native to the Amazon basin. Due to a taxonomic shift in 2009 when C. batesii was declared a distinct species from Corallus caninus, research on the basic biology and behavior of C. batesii and other Corallus spp. has become muddled. This study contributes to clarifying the biology of C. batesii by analyzing the temporal, foraging, and spatial behavior of six juveniles in a captive setting at Zoo Atlanta. Video recordings were collected over the course of two feeding cycles. On predetermined days, six hours of data were coded for every individual with an equal examination of behavior during daylight and nighttime hours. Spatial data were collected after individuals transitioned from movement into stationary behaviors. Results show that hunting and movement behaviors were primarily nocturnal while resting behaviors were diurnal. Qualitatively, site fidelity was observed in individual snakes with respect to both hunting and resting behaviors. |
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10. 11:50 VIRTUAL Integrating Radio Telemetry and Accelerometry to Examine the Effects of Roadways on the Movement Behavior of Timber Rattlesnakes (Crotalus horridus). Anna Tipton*, Georgia College & State University; Dominic DeSantis, Georgia College & State University anna.tipton@bobcats.gcsu.edu
Roadways are among the most widespread anthropogenic land use features that impact wildlife. Negative impacts include vehicle-induced mortality, habitat degradation and fragmentation, and the disruption of movement. Conversely, roadways can also create edge habitat that might offer benefits to many species. We are using a novel integration of emerging spatial analyses and tri-axial accelerometry to evaluate the impacts of roadways on the movement behavior of Timber Rattlesnakes (Crotalus horridus) from central Georgia. Dynamic Brownian Bridge Movement Models are employed to calculate motion variance and estimate utilization distributions (UDs) for individual rattlesnakes. Accelerometers simultaneously enable quantification of long-term, continuous activity budgets for interpreting fine-scale temporal movement patterns. Relating spatial metrics to Mean Distance to Roadway (MDR) revealed no significant associations when considering the full sample. However, sub-setting by sex revealed a significant positive linear relationship in males between MDR and Distance Per Movement and UDs. However, no significant relationships were detected between mean Hours spent Moving per Day and MDR within male or female snakes in our current sample. This might reflect that roads are spatially, but not temporally, restricting movement by males in our sample. However, potential edge effects of roadways, including the possibility of increased rodent density and thermoregulatory benefits, could contribute to the decrease in spatial metrics for males in close proximity to roads. We anticipate that ongoing radio telemetry-accelerometry monitoring and quantification of potential edge effects will refine these preliminary findings. |