Jorge Daniel Williams

Herpetofauna, Coastal Dunes, Buenos Aires Province, Argentina

Coastal dunes habitats at Buenos Aires province are in a fragmentation and habitat loss process due to related human activities. Knowledge on the herpetofauna of Buenos Aires province coast habitats is plentiful for some species of lizards and scarce for most amphibians and snakes. With the aim to present a list on the amphibians and reptiles of the coastal dune habitats in Buenos Aires province we recorded species coming from field work, cited in literature, and vouchers specimens deposited in herpetological collections. We recorded 35 species in six sectors that represent the last remnants of coastal dunes in good conservation status. The Mar Chiquita and Faro Querandi Reserves represent an important contribution to the conservation of several species that inhabit coastal dune habitats. It is necessary to increase the knowledge on biodiversity in those habitats in order to develop conservation strategies.

Methods for Assessing Population Size in Sand Dune Lizards (Liolaemus Multimaculatus)

Abstract Basic information, such as population size and density, is needed for conservation and management of many species, especially threatened species. Thus, well-designed population monitoring programs that use appropriate methods for estimating parameters of interest, including density and survival, are needed as well. Mark-recapture and distance-sampling are established methods for estimating density in wildlife surveys. The sand dune lizard (Liolaemus multimaculatus) is an endemic and vulnerable species that inhabits dune habitats in Argentina. At present, however, there are no accurate estimates of density of this species and no established monitoring programs. The objectives of this study were (1) to test the use of mark-recapture and distance-sampling methods and (2) to estimate density of this species in Mar Chiquita Reserve (37° 37′ S–57° 16′ W), an important area for the protection of this species. For distance-sampling surveys, we used a systematic line-transect design; for mark-recapture sampling, we performed exhaustive surveys and captured, marked, and recaptured lizards manually. Based on distance-sampling, populations were estimated at 3.6 and 5.4 individuals per ha in 2007 and 2008, respectively; corresponding estimates based on mark-recapture data were 5.2 and 4.1 individuals per ha in 2007 and 2008, respectively. Detection probabilities were 0.23 in both 2007 and 2008 distance-sampling analyses and capture probabilities were 0.02 and 0.05 in 2007 and 2008 mark-recapture analyses. Based on these estimates, the Mar Chiquita Reserve contains a population of at least 10,000 individuals. Both methods were adequate for estimating populations of sand dune lizards, given the facility with which individuals can be detected and captured. The distance-sampling method requires less effort, but the mark-recapture method allows estimates of survival as well as density. Results of this work provide the baseline for developing a monitoring program for this lizard, and we suggest that the distance-sampling method be used to monitor all populations of sand dune lizard.

Selection of key features of vegetation and escape behavior in the Sand Dune Lizard (Liolaemus multimaculatus).

Vegetation structure and cover are two of the main factors which determine microhabitat preferences in lizards. The Sand Dune Lizard (Liolaemus multimaculatus) is a vulnerable and endemic species of the pampean coastal habitats from Argentina. We hypothesized that: a) Sand Dune Lizard prefer to perch in microhabitats that offer a good balance between visibility and refuge, and; b) lizards prefer microhabitats in which plant types allow them to resort to sand burying behavior. We recorded data of microhabitat (bunch-grasses sizes and plant types) used by lizards (males, females and juveniles) in a population at the Mar Chiquita Provincial Nature Reserve. We applied the use-availability design to assess preferences. We evaluated differences between sex and relation between sizes of lizards. Lizards preferred bunch-grasses of intermediate size. Habitats conformed only by herbaceous species were the most preferred by lizards. We did not find differences between males and females, neither relations between size of lizards and the tested variables. Adult lizards of both sexes use bunch-grasses more frequently than juvenile individuals. The preferences for herbaceous species could be related to the sand-bury behavior that lizards use to escape from predators. More studies are necessary in order to assess the processes related with habitat preferences

Southernmost Localities of Trachemys dorbigni and First Record of Trachemys scripta elegans for Argentina (Cryptodira: Emydidae)

Abstract We report two new localities for Trachemys dorbigni that expand the southern range border for approximately 120 km. These new localities are Arroyo Buñirigo and Arroyo Zapata. Both are streams related to the Río de La Plata shoreline at Buenos Aires province, Argentina. We also record the nonnative Trachemys scripta elegans for the first time for Argentina.

Ampliación del conocimiento sobre uso de hábitat en Liolaemus multimaculatus, sitios de fuga

The knowledge about spatial preferences in animals represents the first stage to understand the interactions between the organisms and its environment. The sand dune lizard (Liolaemus multimaculatus) is a species highly adapted to live in the sand. The goal of this work was to study the habitat use in different moments/situation during its period of activity, in order to obtain a more understanding about spatial preferences in this species. Models based on the use vs availability criterion were applied in order to assess the preferences for sites used as refuge and to compare those sites with perch sites. The models shows differences between use and availability and also differences between perch sites and refuge sites were observed. Results shows that this species used a great diversity of microhabitats with a high reject for microhabitats without vegetation cover. The conservation of good habitats for this species must consider both kinds of microhabitats, those used for thermoregulation and feed and those others used for refuge.

Squamata, Scincidae, Mabuya dorsivittata (Cope, 1862): distribution extension in Buenos Aires province, Argentina

Mabuya dorsivttata is a lizard with a wide distribution in South America. In Buenos Aires province, Argentina, previous voucher records exist only from its northern sector and from Mar del Plata city. In this work, two new records of M. dorsivittata from Buenos Aires province are presented: (1) Azul city (36°46’50” S, 50°51’10” W) and (2) Mar del Tuyu city (37°20’08” S, 59°07’60” W). These new records are located about 175 km from the nearest previous record.

Reproductive Biology of the Critically Endangered Valcheta Frog, Pleurodema somuncurense (Anura: Leptodactylidae), from Patagonia, Argentina

Abstract. Amphibians exhibit a great diversity of reproductive modes. Nevertheless, reproductive biology is still unknown for several threatened Neotropical species, including the Critically Endangered microendemic Valcheta frog, Pleurodema somuncurense. This paper looks at the reproductive biology of this species, describes its behavior, amplexus, spawning, clutches, embryonic development and breeding microhabitats, and discusses differences and similarities between it and the other Patagonian species included in the P. thaul clade: P. bufoninum and P. thaul. Fieldwork was conducted from 2013–2015 in the headwaters of Valcheta Stream (northern Patagonia, Argentina), over the whole known range of P. somuncurense. We also added information from an ex situ survival colony of this species. Pleurodema somuncurense has prolonged seasonal reproductive activity during spring-summer and presents features of both explosive and prolonged breeders. The Patagonian species of the P. thaul clade all have inguinal amplexus and lay pigmented eggs in gelatinous strings. During inguinal amplexus, the male P. somuncurense arches its body, bringing its vent closer to the females, while contracting its body muscles rhythmically and moving its pelvic girdle up and down while the female spawns the eggs. We occasionally recorded mating calls, release calls, and warning vibrations. Although there are similarities among the three species, P. somuncurense has some specific features, such as scramble competition, which has not yet been recorded for any other species in the genus, and the mating call, although better records in natural conditions are needed for detailed analysis and more robust comparison. Because the breeding microhabitats used by P. somuncurense are currently under disturbance from livestock, their protection should be a matter of concern.

First natural endocranial cast of a fossil snake (Cretaceous of Patagonia, Argentina)

In this study, we describe a natural endocranial cast included in a partially preserved medium-sized skull of the Upper Cretaceous South American snake Dinilysia patagonica. The endocast is composed of sedimentary filling of the cranial cavity in which the posterior brain, the vessels, the cranial nerves, and the inner ear surrounded by delicate semicircular canals, are represented. It is simple in form, with little differentiation between the three main areas (Forebrain, Midbrain, and Hindbrain), and without flexures. The nervous system is well preserved. The posterior brain surface is smooth, except for two small prominences that make up the cerebellum. A large inner ear is preserved on the right side; it consists of a voluminous central mass, the vestibule, which occupies most of the space defined by the three semicircular canals. In particular, the lateral semicircular canal is very close to the vestibule. This characteristic, in combination with the medium to large body size of Dinilysia, its large skull and dorsally exposed orbits, and vertebrae bearing a rather high neural spine on a depressed neural arch, suggests that this snake would have had a semifossorial lifestyle. Anat Rec, 2017.

A management strategy for the long-term conservation of the Endangered sand-dune lizard Liolaemus multimaculatus in the Pampean coastal dunes of Argentina

The sand-dune lizard Liolaemus multimaculatus is an Endangered species endemic to the Pampean coastal dunes of Argentina. To inform the development of a future Action Plan for this species, we investigated the demography and conservation status of all remaining populations, and we suggest management actions appropriate to local needs. We used population viability analysis to assess extinction risk in three inbreeding scenarios and estimate the minimum viable population and the minimum area requirement. To assess the current status of each local population, we used information related to population size, human pressure and connectivity. The results were then used to set and prioritize conservation management actions at local level. Our models indicated that populations of > 2,400 individuals would be viable in the long term and that inbreeding depression has a strong effect on extinction risk. The southern patches of coastal dune contain the largest populations of sand-dune lizards, and they are also better connected and less threatened. We suggest land protection as the priority management action for populations larger than the minimum viable population, whereas habitat recovery, when possible, should be the priority for patches of coastal dune smaller than the minimum area requirement. Supplementation with a small number of individuals could stabilize unviable populations but should be considered only in certain situations. The long-term conservation of the sand-dune lizard will be feasible only if a conservation action plan is developed and implemented.

Asociación Herpetológica Argentina: Treinta años de esfuerzos y resultados

Fil: Williams, Jorge Daniel. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Division Zoologia de Vertebrados; Argentina; Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico La Plata; Argentina;