Alligators prefer marsh with water salinities of less 

 than 10 °/oo (Chabreck 1971b). Saltwater intrusion is 

 particularly detrimental to young alligators (Joanen 

 and McNease 1972b). Structures which stabilize water 

 levels will decrease nest loss by flooding and reduce the 

 effects of drought. Weirs may be desirable for stabili- 

 zing water levels (Chabreck and Hoffpauir 1962). Marsh 

 drainage sholild be avoided altogether and shading vege- 

 tation should be retained (SpotUa et al. 1972). 



A strictly regulated harvest has become an integral 

 part of alligator management in some portions of the 

 Chenier Plain region. In addition to providing econo- 

 mic benefits to the people of the area, a harvest serves 

 to regulate the numbers of animals. In some places, ani- 

 mals are so abundant that they are rapidly becoming a 

 nuisance and a hazard. The 1970 session of the Louisi- 

 ana State Legislature enacted laws setting up the frame- 

 work for an alligator harvest. By 1972, a harvest plan 

 had been developed, and in the late summer of that 

 year, the plan was implemented. Palmisano et al. 

 (1973) provided a thorough analysis of the first experi- 

 mental harvest program. The harvest regulations are 

 designed to be selective for adult males and regulate 

 the harvest according to the abundance of alligators 

 within marsh types. 



Nichols et al. (1976) developed a model simulating 

 the dynamics of a commercially harvested alligator 

 population inhabiting the privately owned coastal 

 marshland of Cameron and Vermilion parishes. The 

 model takes into consideration all known aspects of 

 the alligator's life history. They believe that under ex- 

 isting habitat conditions, a base population of 100,000 

 animals could be maintained for at least 20 years when 

 subjected to an annual differential (selective for adult 

 males) harvest rate slightly greater than 5%. 



Most of the privately owned marshes of Cameron 

 Parish (1 12,660 ha or 278,270 a) have had an alligator 

 season since 1972 (excluding 1974). Portions of Ver- 

 milion (106 ,600 ha or 263, 302 a) and Calcasieu parishes 

 have been opened to alligator hunting in subsequent 

 years. This harvest apparently had no detrimental 

 effect upon the alhgator population (Palmisano et al. 

 1973). 



Marsh water levels are critical to the Chenier Plain 

 alligator population. High water during June, July, and 

 August is a major cause of egg mortality. Nichols et al. 

 (1976) reported that egg mortality from flooding be- 

 gins with marsh water depths in the nests of 27 cm 

 (10.5 in) and virtually all nests are destroyed at a depth 

 of46cm(18in). 



Drought increases mortality through dessication, 

 predation, and cannibalism, and magnifies the effect of 

 Ulegal hunting by concentrating many animals in easily 

 accessible water bodies. Lack of open water for court- 

 ship during the spring breeding season results in re- 

 duced reproduction (Joanen and McNease 1970, 1972a, 

 1975). 



Salinity limits the distribution of alligators in 

 marsh habitats. The species has a low salt tolerance and 

 is generally restricted to areas having salinities less than 



10 '/oo (Chabreck 1971b). Salt water intrusion is par- 

 ticularly detrimental to young animals in some areas 

 (Joanen and McNease 1972b). 



5.4.2 WESTERN COTTONMOUTH (Agkistrodon 

 piscivorus) 



Most published reports on movements are con- 

 cerned with overwintering congregations, water fluctu- 

 ation responses, road-crossing observations, or feeding 

 aggregations. In south Louisiana, cottonmouths may 

 congregate on or near higher ground (cheniers, levees, 

 spoil banks) during colder months or during spring or 

 hurricane flooding. They usually disperse when warmer 

 weather arrives or when flood waters recede. 



Large assemblages may also be encountered 

 around shallow marsh or swamp pools during warm 

 summer nights. In traveling Chenier Plain Route 82 

 from Pecan Island to Cameron, Louisiana, it is not un- 

 common to see a dozen or more individuals crossing 

 the road, night or day. Duck hunters in Sabine Nation- 

 al Wildlife Refuge reported snakes moving into vegeta- 

 tion near their blinds, apparently for sunning purposes. 

 Keiser (1974a, 1976a) noted responses to water fluctu- 

 ations and to overwintering sites in the Atchafalaya 

 wetlands. Arny (1948) reported movements in adjust- 

 ment to seasonal changes in water levels and observed 

 cottonmouths frequenting 'drift' along ridges during 

 high water. These snakes dispersed over the marshes 

 with the lowering of water levels during the summer. 

 More detailed comments on daily and seasonal move- 

 ments are found in Barbour (1956), Wright and Wright 

 (1957), Burkett (1966), and Wharton (1969). 



Cottonmouths may be found in most of the Che- 

 nier Plain habitats. They may be expected in and ad- 

 jacent to rivers, bayous, swamps, marshes, marsh ponds, 

 tidal ditches, and the Intracoastal Waterway. They are 

 also found along chenier levees and spoil banks, within 

 woodlands of various vegetational types, and in poorly 

 drained areas and water-filled ditches of agricultural 

 and urban areas. Cottonmouths are commonly asso- 

 ciated with bodies of water, but they may wander over- 

 land for considerable distances. They are encountered 

 occasionally in brackish habitats, but only rarely in or 

 near waters of higher salinity. They are known to uti- 

 hze animal burrows (those of crayfish and armadillos) 

 and to submerge below the waterline in these burrows. 

 They will also bask in bushes and trees over the water, 

 sometimes moving as high as 2 to 3 m (6 to 10 ft) 

 above the waterline. 



Published locality records of cottonmouths in the 

 Chenier Plain are not common. Burt and Burt (1929) 

 noted a specimen from Vidor in Orange County, Texas. 

 Brown (1950) included these species on his list of 

 Texas coastal prairie species and reported three in Jef- 

 ferson County. Burkett (1966) remarked that he had 

 "twice observed cottonmouths crawling into crayfish 

 burrows along the Gulf Coast of Texas . . ." Raun and 

 Gehlbach (1972) and Werler (1970) showed distribu- 

 tion records for Orange, Jefferson, Chambers, and Gal- 

 veston Counties in eastern Texas. For the Louisiana 

 Chenier Plain, Penn (1943) reported 25 cottonmouths 



249 



