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How to Measure a Bat Youth's Size

For researcher's studying bats, it is often necessary to measure their size. These measurements will give the researcher an idea of the bat's age. Determining the age of a young bat by its size depends on what species it is, and growth tables can be found in scientific literature. Taking the measurements is relatively straight-forward, but because of the risk of rabies, the handling of bats should only be done by a researcher with the proper training and an up-to-date rabies vaccination. Wearing gloves is not recommended because of the need to handle the bats gently to avoid injuring them.

Things You'll Need

Cloth bag
Scale
Ruler
Caliper

Instructions

- 1
  Place the bat inside a cloth bag and place that onto the scale. Make note of the weight, then remove the bat from the bag and weigh the bag alone. Subtract these two weights to get the weight of the bat alone.
- 2
  Hold the bat with your thumb on its back and its body resting on your other fingers. Carefully pull one of the bat's wings away from its body to measure its radius. The radius is the arm bone that corresponds to a human's forearm. Hold the ruler against the bone and make a note of its length.
- 3
  Wrap your fingers around the bat and gently hold it with its wings held tucked in next to its body. Take a measurement of the bat's body length by holding it against the ruler, and measuring it from the tip of its nose to the tip of its tail pulled out straight.
- 4
  Measure the height of the bat's ear, using the caliper. Hold the tip of the caliper's fixed jaw against the top of the bat's ear, and turn the fine adjustment wheel to move the sliding jaw down to the base of the bat's ear. Read the measurement off of the caliper's scale.
- 5
  Measure the height of the tragus, again using the caliper. The tragus is the flap of skin in the middle of the bat's ear, and knowing its size can help in the differentiation of bat species.
- 6
  Hold the bat against the ruler and spread its wings to their full length, being careful not to hold the bat by its wings alone. This step may require the help of an assistant to hold the bat while you extend its wings. Make a note of the bat's wingspan from wingtip to wingtip, including the width of its body.
- 7
  Press the ruler against the bat's body with the end of the ruler against the base of the bat's tail to measure the length of its tail vertebrae. It is important to know the length of the tail to accurately determine the bat's body size.

Animals & Science