|SREL Reprint #0960|
of Climatic Factors Influencing Migrations of the Salamander Ambystoma tallpoideum
Migrations of breeding adult and metamorphosing
juvenile mole salamanders, Ambystoma talpoideum, were studied in
five populations in South Carolina from Sept. 1978 through July 1982.
At each breeding site immigrations and emigrations were monitored through
the use of terrestrial drift fences with pitfall traps.
Onset of breeding immigrations occurred as early as Sept. but migrations
“enmasse” did not occur until Nov., Dec., or Jan. Onset of breeding migrations was not related to a threshold
temperature or to a threshold amount of rainfall. However, breeding migrations always occurred during the
coldest but not necessarily the wettest months of each year. Time of peak migration varied annually depending upon
meteorological conditions. Total
number of breeding adults or breeding population size, was significantly
correlated with cumulative rainfall during the time of immigration but not to
total days of rainfall or to total days below 0 C.
Sex ratio of immigrating adults was significantly biased towards males at
the beginning of the breeding season whereas by the end of the season it was
biased towards females. Emigration
of adults from the breeding sites occurred each March and was consistent among
sites and years. After a minimum
larval period of four months, metamorphosing juveniles would emigrate from the
pond as early as May and continue until the breeding site dried.
In relatively permanent breeding sites emigration of metamorphosing
juveniles usually continued through Oct. However,
most larvae did not metamorphose but remained instead in the ponds and matured
sexually. During the very dry year
of 1980-81 water levels in two relatively permanent breeding sites were
substantially reduced when compared to previous years.
This drying process probably induced metamorphosis and emigration of
sexually mature gilled morphs.
Statistical models which predict the magnitude of
migrations indicated that rainfall, water level, and minimum air temperature
were consistently important environmental variables. Multiple regression models using these three environmental
variables explained 17-55% of the variation in number of migrating salamanders
each day. Unquantified factors such
as duration of rainfall, time of day of rainfall may be responsible for some of
the remaining variation.
SREL Reprint #0960
Semlitsch, R.D. 1985. Analysis of climatic factors influencing migrations
of the salamander Ambystoma talpoideum. Copeia 1985:477-489.