Techniques for Reptiles in Difficult- To- Sample Habitats
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CHAPTER ELEVEN Techniques for Reptiles in Diffi cult- to-Sample Habitats ROBERT E. LOVICH Chapter Coordinator Overview Robert E. Lovich / 167 this chapter are working to develop novel sampling strategies Rock- Dwelling Reptiles Robert E. Lovich and Aaron M. Bauer / 167 or to improve existing ones. Without doubt, readers of this Snake Hibernacula and Communal Denning Robert N. Reed, chapter will also develop new strategies. Whether reptiles live Cameron A. Young, and Robert T. Zappalorti / 171 underwater, underground, high in a forest canopy, sheltered within a mountain of rock, or in some other seemingly inac- Arboreal Reptiles: Tree-Trunk and Canopy- Dwelling cessible place, they can be repeatedly and successfully col- Species Indraneil Das / 175 lected and/or detected with methods currently available. Swamp- Dwelling Crocodilians William E. Magnusson / 179 Detecting and Capturing Turtles in Freshwater Habitats Richard C. Vogt / 181 Rock- Dwelling Reptiles Alternative Methods for Sampling Freshwater Turtles and Robert E. Lovich and Aaron M. Bauer Squamates Thomas S. B. Akre, John D.Willson, and Thomas P. Wilson / 187 Sampling reptiles in rocky habitats is challenging. The dense and impenetrable nature of piles of rocks and boulders makes Sampling Marine and Estuarial Reptiles Harold K. Voris and it diffi cult to locate and extract reptiles living within and John C. Murphy / 192 among them. When searching for or monitoring saxicolous reptiles (from the Latin saxum, meaning rock, and –cola, meaning inhabitant; syn. rupicolous from the Latin rupes, also Overview meaning rock), it is important to determine how the target Robert E. Lovich species use the habitat and how their natural histories relate to it. Rocky habitats can provide reptiles with protection This book deals with sampling and other aspects of fi eld re- from predators, refuge from the physical environment, forag- search on reptiles. Not surprisingly, the disparities in size and ing sites (including for preying on other saxicolous animals), methods of locomotion between reptiles and humans con- and breeding and denning sites; they can also contribute to strain the ability of the latter to sample the former and often reptile thermoregulation (Cowles and Bogert 1944; Huey interfere with the regular, methodical collection of informa- et al. 1989; Webb and Shine 1997, 1998a, 1998b, 2000; Kearney tion (capture or observation) that scientifi c protocols and 2002; Shah et al. 2003, 2004; Quirt 2006). Many rock- dwelling methodologies require. The partial or complete inability of species prefer or are completely restricted to a par tic u lar type humans to negotiate certain types of habitat (e.g., deep water, (or types) of rock (e.g., granite, sandstone, limestone, etc.) or unstable rock piles, treetops) and/or the ability of reptiles sim- rock crevice, because of its size, exposure, thermal qualities, or ply to avoid detection and capture in some habitats put humans other features (Schlesinger and Shine 1994a, 1994b; Bauer and at a disadvantage compared to reptiles that are well adapted Sadlier 2000; Lovich 2001). Indeed, expansive rocky habitats to their par tic ular habitats. In this chapter, we deal with sam- that appear uniform to an untrained human observer gener- pling methods and procedures for a subset of habitat types in ally provide a diversity of discrete types of microhabitat for which we believe reptiles to be especially diffi cult to sample. saxicolous reptiles. The long- term stability of the rock habitat While we do not provide comprehensive coverage of all the and its evolution are also important considerations. Some diffi cult-to- sample habitats or reptiles, we present wide taxo- nomic and geographic coverage, along with a host of refer- Reptile Biodiversity: Standard Methods for Inventory and Monitoring, edited by ences useful for a project designer. We also provide names of Roy W. McDiarmid, Mercedes S. Foster, Craig Guyer, J. Whitfi eld Gibbons, individuals from whom additional information on sampling and Neil Chernoff. Copyright © 2012 by The Regents of the University of strategies may be sought. Many of the authors represented in California. All rights of reproduction in any form reserved. 167 From Mercedes Foster and Roy McDiarmid, Reptile Biodiversity, Berkeley and Los Angeles: University of California Press, 2012. species require geologically old and stable exfoliating rocks agencies expressly forbid the use of equipment to break or such as those along high ridges or on tops of hills, in contrast move rock piles for collecting purposes. An investigator to the more dynamic habitats in valleys and canyons that should thoroughly review local laws and regulations before may be seasonally fl ooded or subject to landslides or tectonic using any tools to facilitate sampling. The surveyor should be activity in some regions (Lovich 2001). mindful that rock fl ipping, in addition to needlessly degrad- Prior to sampling an area for saxicolous species, the inves- ing or destroying habitats when recklessly employed, is po- tigator should thoroughly understand the thermal require- tentially detrimental to resident species in other ways. Acci- ments of the target species and the temperature range and dentally crushing animals when lifting or moving rocks is seasons within which it is active. Successful location or moni- always a possibility; however, crushing what lies beneath a toring of species can be maximized by searching during their rock can be minimized by lifting the rock slowly and cau- specifi c daily and seasonal activity periods. Saxicolous habi- tiously and looking for reptiles underneath, as you lift. After tats can be sampled in a variety of ways. The methods de- a rock is lifted a few centimeters, it can be wedged in position scribed below are by no means comprehensive, but they should with a small stone and the area underneath it searched with provide an overview of techniques to be considered when the aid of a fl ashlight or mirror. Many rocky habitats are the developing the sampling plan for a project. Additional infor- result of thousands of years of weathering, and moving rocks mation about fi eld techniques relevant to saxicolous reptiles that are tightly pressed together can break the moisture seal can be found in Simmons (1987, 2002) and Bennett (1999), created by mosses, lichens, and detritus that have accumu- and in Chapter 5, “Finding and Capturing Reptiles,” and lated along the rock margins. A moisture seal can be critical Chapter 13, “Standard Techniques for Inventory and Moni- for animals trying to avoid desiccation, and it can insulate toring,” in this volume. The specifi c sampling method or them from extreme outside temperatures. It can also prevent methods to be used should be chosen carefully to maximize rainwater from periodically fl ooding a rocky refugium. Once sampling effi ciency. a rock is removed from its original location, the microhabitat that was present beneath it will be altered signifi cantly. Habi- tat disruption can be minimized if rocks that are moved are Rock Flipping returned to their original positions. We exhort anyone using manual rock fl ipping methods to “always put the rocks Manual rock fl ipping is a pop ular and widely used method for back!” sampling reptiles in saxicolous habitats. This method involves moving or lifting rocks— including rock sheets or fl akes— to expose reptiles that may be hidden beneath or within them. Visual Surveys Rock fl ipping is most useful when collecting specimens, but the technique can be used to gather baseline data or to com- Investigators carry out visual surveys for saxicolous species pile a species list for a par tic u lar area. It is an effective way for to document the presence or absence of species as part of a surveyor to search through rocks at the surface or subsurface transect surveys, visual encounter surveys, or other moni- level, and it has been utilized extensively by herpetologists. toring protocols (see Chapter 13, “Standard Techniques for When employing this method, investigators should consider Inventory and Monitoring”). Simply walking through an and record the microhabitat used by the target species, be- area and noting the location of reptiles during the day or at cause many reptiles prefer par ticu lar types of rock-crevice night can provide data on species’ distributions and their habitat (Figs. 55 and 56). Whether the rocks lie on dirt or on presences or absences at partic ular sites or in par tic ular mi- other rocks, whether they are vertical or horizontal, their crohabitats. Such data can be used to develop a reptile spe- slopes, aspects, and thermal characteristics, as well as the cies list for an area. Reptile sign, such as feces or shed skin, amount of space beneath them, are all important consider- can also be used to identify the presence of certain species. ations that can help to maximize search effi ciency and mini- Droppings at or near the apex of exposed rocks with a view mize search effort and habitat disturbance when looking for often signal the presence of males of territorial diurnal liz- specifi c species. Field investigators should also be aware that ards. In contrast, large accumulations of feces or nitroge- repeated sampling or collecting in the same rocky habitats has nous waste near crevice openings or overhangs suggest the been shown to result in fewer reptiles and decreased relative presence of nocturnal forms, such as geckos. Rupicolous abundance, and to have impacts on reptile species, sex, age- snakes often use crevices or rock edges to assist in the re- class, and seasonal use (Goode et al. 2004, 2005). moval of skin in ecdysis. Shed skins found in crevices or One constraint on rock fl ipping is the size of rock that the between rocks can provide species- level identifi cation if surveyor can lift. Large rocks or boulders, as well as smaller they are reasonably intact.