Monitoring cryptic amphibians and reptiles in a Florida state park

We monitored cryptic herpetofauna at Savannas Preserve State Park, Florida, by combining artificial cover counts with a quantitative paradigm for constructing and calculating population indices. Weekly indices were calculated from two consecutive days of data collection each week for 7 months from mid-winter to mid-summer in three habitats. Seventeen species were observed at least once, and time trends using index values were followed for six species. Among these, abundance and seasonal pattern information were obtained for an exotic species (greenhouse frog) and a species identified by the Florida Committee on Rare and Endangered Plants and Animals as threatened (Florida scrub lizard). We identified winter as the optimal time in this area to monitor populations for conducting annual assessments. This combined observation and indexing approach could provide managers or researchers with an economical means to quantitatively index population trends for multiple cryptic herpetofauna species simultaneously. Using artificial cover to sample within a population indexing design can be generalized beyond monitoring herpetofauna. Other forms of artificial cover that can be used as observation stations include aquatic artificial substrates, artificial tree cavities, artificial reefs, and other artificial aquatic structures and artificial sea grass units, among many others, and a wide range of taxa are suitable for population monitoring using artificial cover as observation stations in the approach we present, including insects, soil invertebrates, micro and macro aquatic invertebrates, fish, crustaceans, and small mammals

A general model for predicting brown tree snake capture rates

The inadvertent introduction of the brown tree snake (Boiga irregularis) to Guam has resulted in the extirpation of most of the island’s native terrestrial vertebrates, has presented a health hazard to small children, and also has produced economic problems. Trapping around ports and other cargo staging areas is central to a program designed to deter dispersal of the species. Sequential trapping of smaller plots is also being used to clear larger areas of snakes in preparation for endangered species reintroductions. Traps and trapping personnel are limited resources, which places a premium on the ability to plan the deployment of trapping efforts. In a series of previous trapping studies, data on brown tree snake removal from forested plots was found to be well modeled by exponential decay functions. For the present article, we considered a variety of model forms and estimation procedures, and used capture data from individual plots as random subjects to produce a general random coefficients model for making predictions of brown tree snake capture rates. The best model was an exponential decay with positive asymptote produced using nonlinear mixed model estimation where variability among plots was introduced through the scale and asymptote parameters. Practical predictive abilities were used in model evaluation so that a manager could project capture rates in a plot after a period of time, or project the amount of time required for trapping to reduce capture rates to a desired level. The model should provide managers with a tool for optimizing the allocation of limited trapping resources. Copyright # 2003 John Wiley & Sons, Ltd

Relating Ten Years of Northern Raccoon Road-Kill Data to Their Attraction to Sea Turtle Nests

One of the primary threats to sea turtle reproduction in Florida is nest predation by Northern Raccoons (Procyon lotor). We examined 10 years of nest deposition data from a high-density sea turtle nesting beach at Sebastian Inlet State Park, Florida, USA, along with data on raccoon road-kills from the adjacent road, and data on park attendance (as an index of local traffic) to make inferences about raccoon activity patterns relative to turtle nesting. Northern Raccoon road-kills diminished during turtle nesting, even though local traffic was higher. Virginia Opossums (Didelphis virginiana), the only other mammal consistently found as road-kills, did not show a decrease during turtle nesting season, but only rarely function as primary predators of turtle nests. We believed the most logical interpretation was that the abundant food resource of turtle eggs attracts raccoons to the beach during turtle nesting and they do not leave the beach area until the nesting season ends. The large numbers of Northern Raccoon road-kills during the fall-winter might be a signal that management actions to protect turtle nests might be needed

Wildlife hazard assessment for Phoenix Sky Harbor International Airport

Abstract We examined wildlife abundance, distribution, and movement patterns at Phoenix Sky Harbor International Airport (PHX) and within an 8-km radius to assess current air-strike hazards, and to provide baseline information for projecting changes in airstrike hazards as land-use patterns around PHX change. We found that water sources at or near PHX especially induced wildlife movement patterns that put air trac at risk. This was particularly true of the Salt River bed adjacent to the airport, which also is a natural¯ight corridor for birds. Compounding the problem, air trac at PHX was the heaviest when bird abundance and activity was the greatest during migration and breeding. We feel that air strike hazards at PHX are likely to increase substantially as the Salt River bed is reclaimed to produce additional lakes and high quality riparian habitat. We oer recommendations to reduce the hazard levels currently found at PHX and to reduce additional hazards as the habitat around PHX is converted and produces more attractive wildlife habitat. Published by Elsevier Science Ltd

Impact on predation of sea turtle nests when predator control was removed midway through the nesting season

The beach at Hobe Sound National Wildlife Refuge (HSNWR) is a high-density nesting beach serving three species of threatened and endangered sea turtles. Historically, up to 95% of turtle nests at HSNWR were lost to predation by raccoons and armadillos. Consequently, predator control was identified as the most important conservation tool at HSNWR, and predator control optimized by predator monitoring led to highly successful results whereby predation had been reduced to low levels (7–13.5% of monitored nests) in 2002 and 2003. In 2004, funding shortfalls caused predator control to be curtailed with ~1.5–2 months remaining in the nesting/hatching season. We analyzed the resulting effects on turtle nest predation levels compared with the results from 2002 and 2003. The predation rate in 2004 compared favorably with that of 2002 and 2003 until the end of June, after which control was curtailed. Thereafter, predation rapidly accelerated, with the 2004 predation rate increasing to 1.5–3 times the rates from 2002 and 2003 by the end of August. The discrepancy in all likelihood would have grown further, except Hurricane Frances destroyed all remaining nests with 1.5–2 months left in the nesting/hatching season. Product-limit survival analyses demonstrated substantial differences in turtle nest survival between 2004 versus 2002 and 2003, but not between 2002 and 2003. When analyzed as cohorts based on month of nest deposition, no differences were found among 2002, 2003, 2004 for nests deposited in May. These nests received full protection from predation in each of the three years. However, the survival analyses for nests deposited in June, and those deposited in July showed inferior survival for 2004 when predator control was removed for the last half of nesting/hatching