Studies on the Growth of Tagged Toads (Bufo terrestris americanus Holbrook)

Abstract

TUDIES on the migrations, growth, homing, and other phases of the life histories of the toads and frogs of the Ithaca, New York, region were begun in 1940. The early report of Wright (1914) furnishes a background for our investigations, in which we have attempted to obtain more detailed information by observations of marked individuals throughout the warmer months and from year to year. Some recoveries were made and additional specimens were marked in 1941 and 1942. The tagging was resumed in 1946, but, although several toads marked sometime between 1940 and 1942 were observed by others, none were captured and measured by us. The toads, all Bufo terrestris americanus Holbrook, the only Bufo found in the Ithaca area, were marked by the use of metal tags locked securely around the lower jaw. This method was successfully used by the senior author (1940) for marking frogs. In 1940 and 1941 only a medium sized tag of satisfactory thickness was available but in 1942 a smaller one, called a fingerling tag,1 was used. It is a much better size for toads and smaller frogs. The toads often pulled at the tags when first inserted but after a few days they appeared to ignore them. Most toads carried the tag in the mouth along side or under the tongue. The growth and behavior of some individuals, especially those marked with the larger tags, are probably affected. Some error is involved in making measurements on living toads. In our practice they are first placed in a sitting position and then pushed downward so that the back is straight and parallel to the steel rule upon which they rest. The length is then taken from the tip of the snout to the posteriormost point between the hind legs. This method was always used in our studies and the same individual made all measurements. In order to check the degree of accuracy of measurement a test was run on 10 tagged toads in which each was taken at random and was measured ten times. The length of small males was repeatedly measured to within ?1 mm. The larger turgid females and biggest males could not be remeasured with as great accuracy and varied ?2 mm. In a recaptured individual this error in measurement may be such as to completely annul the growth increment. However, in dealing with large numbers this error probably tends to average out.