52 David Scott 



STUDY AREA AND METHODS 



I observed active hognose snakes while on a preliminary visit to 

 Assateague Island on 18 April 1981. The vegetation of Tom's Cove 

 Hook consists of discrete zones of sand-dune, shrub, grassland, and 

 salt-marsh habitats. Few snakes were observed in shrub and grassland 

 areas during preliminary sampling, and none were seen in the salt 

 marsh. Therefore, systematic sampling was confined to the sand-dune 

 habitat on the inland dune ridges that form a nexus on the spit. These 

 ridges were searched two or three times per week (22 days) from 1 1 June 

 to 12 September 1981. The sequence in which the dunes were searched 

 was varied. The first five searches lasted from 0800 to 1930. No snakes 

 were observed during midafternoon hours, and subsequent sampling 

 was confined to morning and late afternoon. On five occasions searches 

 were conducted for a 3-hour period after sunset. 



The following data were recorded for each capture: date, time of 

 capture, exact location on the dune lines, temperature of the substrate 

 (52 captures only), color of snake, snout-vent length (SVL) to the near- 

 est 0.5 cm, body mass (g), number of dorsal blotches, and number of 

 ventral and subcaudal scales. Each individual was marked with a unique 

 identification code (ID) by clipping two subcaudal and three ventral 

 scales. For recaptured individuals, the linear distance traveled between 

 captures was estimated from an aerial photograph of the site. Sex (Fig. 1) 

 was determined by an analysis of ventral and subcaudal scale counts 

 (Edgren 1961). Five of the snakes that were classified as males according 

 to scale count were noted to have everted hemipenes during handling, 

 supporting the assumption that sex can be determined by scale count. 



RESULTS AND DISCUSSION 



A total of 66 individuals were captured, with 6 individuals (9.1%) 

 recaptured an average of 17.5 days after initial capture. More males (N 

 = 38) were captured than females (N = 28), but the ratio did not differ 

 from 1:1 (x 2 = 1.52, df = 1, p >0.10). Distance moved between captures 

 ranged from 40 to 760 m (x= 390 m). The recapture data were not 

 appropriate to derive an estimate of actual population density (White et 

 al. 1982). However, there are approximately 13.6 ha of habitat suitable 

 for hognose snakes (excluding salt marsh and aquatic sites) on the spit. 

 Using only the 66 individuals captured, the absolute minimum popula- 

 tion density of H. platy rhinos was 4.8 snakes/ ha. 



Two hatchlings were found dead on the road on 15 and 19 August, 

 and were 18.5 and 19.0 cm SVL. No hatchlings were captured during 

 the late summer, so their growth rate could not be determined. Two 

 juvenile males (SVL < 36.0 cm) and one adult male (62.0 cm SVL) were 

 recaptured more than a month after initial capture. These two size 

 classes exhibited average summer growth rates of 2.2 and 1.0 cm/ month, 

 respectively. Piatt (1969) observed higher growth rates in H. platyrhin- 

 os juveniles (3.4 cm/ month) and lower rates in large males (0.8 

 cm/ month). Growth rates for female size classes could not be determined. 



