Research Methods Lab 
 

Goals: Herpetologists use many different methods to conduct their research. This lab will introduce you to some common practices used in the capture, identification and measurement of herpetofauna.

*Note: some of the equipment used in this lab is expensive. You break it, you bought it. 
 

I. Capture 
 

Drift Fence/Pit fall traps

Essentially self explanatory. A drift fence is a short fence which is usually made from some sort of tarp or hardware cloth material, erected with stakes through an area of interest. The pit fall traps can consist of containers such as coffee cans or buckets which are placed at intervals along the fence. The idea is the animal will be moving, hit the fence, begin to follow it and drop into one of the traps. These work quite well for salamanders, small lizards and snakes, and amphibians (if placed near water).  
 

Aquatic Traps

Hoop Traps: Usually made of nets or mesh of varying fineness. Narrow throats at each end allow the animal to swim in, but often prevent it from getting back out. Ideal for catching aquatic turtle species. Can also be used for aquatic snakes and amphibians. Traps can be baited or un-baited.  Canned sardines seem to work quite well for trapping many aquatic turtle species. Commercially available minnow traps work along the same premise and can be useful for capturing smaller herps. 

Fyke Nets: Large aquatic trap consisting of 3 “arms” of netting that extend from a hoop trap like collection chamber. The animal swims into one of the “arms” and is funneled into the trap. Fyke nets are useful for catching rare species, or those not typically attracted to bait. Often, large amounts of “by-catch” accumulate in the trap as all aquatic species will often become entangled in the net. This can include fish, aquatic birds, unwanted herp species, and even the occasional mammal. 
 

Coverboards

Coverboards can be a useful tool in the capture of snakes. They are usually made of wood or corrugated tin and can be placed by researchers in areas of interest to hopefully attract snakes of all types looking for a refuge. Often, the boards attract small mammal species, which may further their ability to attract snakes. Success with coverboards seems to be mixed. With species such as the Kirtland’s Snake (Clonophis kirtlandi) coverboards placed at crayfish burrows during the appropriate season are the most reliable way to find individuals. Species such as the Eastern Massasauga Rattlesnake (Sistrurus catenatus catenatus) seem un-attracted to coverboards in the state of Illinois, but can be reliably located under them in Ohio.    
 

Visual Encounter Survey (VES)

Finding many species of herps involves nothing more than going out, walking around, and looking for them. A VES can be conducted in a regimented way with transect lines and time limits, or it can be done loosely, in a somewhat random “wandering” pattern through a habitat area. Before conducting a VES, the researcher should become familiar with the ecology of the species of interest to best target habitat areas likely to contain that species, as well as the best time of day to look for the species and if they are likely to find animals moving, sitting still, under vegetation, in trees, etc.   
 

Spotlighting

This is a technique used to locate crocodilians at night. The researcher(s) drives around in a boat, shining the spotlight at the water. Crocodilian eyes glow red-orange in the light.  
 

Noosing

This technique is commonly used to capture small lizards. A small noose made of fishing line or stiff thread is tied onto a pole, slip the noose over the lizard’s head and jerk the pole slightly upward. Takes some practice, but can be very effective.  
 

II. Measurement 
 

Sex Probing

Unlike many bird species, herps (particularly snakes) are sometimes not sexually dimorphic in ways that make for easy visual identification of the sexes. Thus, sex of some herps must be determined by insertion of a small probe into the cloaca. GENTLY insert the probe into the cloaca in the caudal direction. If the probe goes in and stops just posterior to the cloacal opening, it is a female. If the probe continues in for several centimeters (due to the presence of hemipenes), it is of course, male.  
 

Snout – Vent Length (SVL)

This is the most common measurement reported in the herp literature. There are several methods employed to measure SVL. The use of a squeeze box is a popular method for keeping snakes still enough to obtain an accurate measurement. A squeeze box is simply a box with some padding at the bottom which the snake is placed into. A weighted piece of plexi glass is then placed over the top of the snake, and a dry erase marker is used to trace the outline of the snake onto the glass. This marker line is then measured with a string or flexible seamstress tape. The other method is to just run the flexible tape along the length of the snake’s (or lizard, or crocodilian) body. Use the measuring tape provided to measure the SVL (to the nearest .1 cm) of one of the live snakes. Be sure to measure from tip of snout down to the vent. To show the amount of error possible when using this technique on live animals, repeat the process until you have 3 measurements within 1cm of each other.    
 

Scale Counts

Probably the most exciting of all morphological measurements! Used most frequently in snakes. Scales counted for research or species ID purposes often include: ventral, subcaudal, and dorsal rows. Smaller head scales can also be counted and used in study. Using one of the live snakes provided, count the ventral (beginning at the “neck” and extending to the vent), subcaudal (from the vent to tip of the tail), and dorsal scale rows (see illustration).  
 
 

Mass

Self explanatory. Mass can be a useful indicator of health or reproductive status. Use the provided equipment to measure the mass of one of the live snakes or turtles.  
 
 

Turtle Specific Measurements

Because of their shells, turtles have their own set of measurements associated with them. Unlike snakes, which are typically measured in centimeters, turtle measurements are taken in millimeters (don’t ask me why, turtle people are weird). Frequently reported turtle measurements include:

Carapace Length (CL) – measured with calipers. Hold the turtle vertically and measure from bottom to top of shell

Carapace Width (CW) – also with calipers but turn the turtle horizontally. Measure at widest part of shell.

Shell Height (SH) – set turtle so plastron rests of bottom caliper. Measure in the center of shell.

Plastron Length (PL) – same as CL but on the plastron

Dome Length (DL) – use flexible tape to measure from mid line of carapace to marginal scutes

Anterior Plastron Width (APW) – measured across pectoral scutes

Posterior Plastron Width (PPW) – measured across femoral scutes

Anterior Plastron Length (APL) – measured from gular to pectoral scutes

Posterior Plastron Length (PPL) – measured from abdominal to anal scutes

Curved Carapace Length (CCL) – measured with flexible tape from top to bottom of carapace, flexing to bend around the curve

Curved Plastron Length (CPL) – same as above, but on the plastron

Left Pectoral Scute (LPECT) – measured along the seam connecting it to right pectoral scute

Annuli- (“growth rings”) if present, measured in left pectoral scute  
 

Use the live turtles and equipment provided to take all of the above measurements. Other measurements (such as shell angles) are also taken by many turtle researchers, but will not be demonstrated here.  
 

III. Identification: Identification of individuals is extremely important to many studies. Thus, several methods have been developed for the easy and reliable identification of individuals in the field.  
 

Scale Clips – Typically a semi-permanent method of marking, scale clips provide an inexpensive way to mark individuals if only short term identification is needed. Using a small, sharp pair of scissors, the researcher carefully cuts a section of section of the ventral scales off. Depending upon how deep the cut is, and how many times the snake sheds, this method of marking may last anywhere from 3 months to 3 years.    
 

PIT tags – PIT stands for Passive Integrated Transponder. These are small tags injected just below the skin which are encoded with a unique number. Using a special scanner to read the numbers, identification of individuals is quick and easy. PIT tags are very versatile and are used for a variety of animals including herps, birds, dogs, cats and other domestic animals, and people. Unfortunately, we can’t let you all inject PIT tags into something, so there will be a demonstration done by the TAs on PIT tag injection.  
 

Shell Notching – The best way to mark a turtle is through the use of shell notches. A small saw is used to cut a square notch into the marginal scutes. A unique combination of notches can be given to each individual, making ID easy by just counting which scutes are notched. Again, we can’t give you all saws and let you notch turtles, so there will be a short demonstration. 
 

Toe Clipping – Used frequently for marking amphibians. Also useful for the collection of material to use in genetic analysis. If used for marking, toes are clipped off in a unique pattern. This technique will not be demonstrated.  
 

Branding/tattooing – relatively new method of permanently marking animals. Tattoos are usually placed on the ventral scales. This technique will also not be demonstrated.   
 

IV. Radio Telemetry

Telemetry is a valuable (although sometimes over-used) tool for gaining insight into the ecology of many animals, including herps. A transmitter is attached or implanted into an individual and a radio receiver and antenna is used to follow the signal to the individual’s location. Satellite towers are also used by some researchers. If the area is large, inaccessible, or it could be dangerous to get too close to the animal, bi-angulation or tri-angulation can also be used. A transmitter has been hidden somewhere outside NRB. Use the provided receiver and antenna to locate it and take GPS coordinates. 

Research Methods Answer Sheet: 
 

II. Measurement 
 

Snake probed ________________________________________Sex________________ 
 

Snake measured_______________________________________ 
 

Write down ALL SVL measurements taken (remember to get 3 within 1cm): 
 
 
 

Snake used for scale counts________________________________________ 
 

Number ventral scales: 
 

Number subcaudals: 
 

Number dorsal scale rows: 
 
 

Snake or Turtle weighed____________________________________ 
 

Mass______________________ 
 
 

Turtle used for measurement______________________________________ 
 

CL__________  APW________  LPECT_________ 
 

CW_________  PPW_________  Annuli:________ ______ 
 

SH__________  APL_________   ________ ______ 
 

PL__________  PPL_________   ________ ______ 
 

DL__________  CCL_________   ________ ______ 
 
 

IV: Radio Telemetry 
 

Where was the transmitter located?___________________________________________ 
 

GPS Coordinates: _________________N ___________________E +/- ____________