HAVE MANY QUESTIONS ABOUT TURTLES
July 19, 2009
How do turtles
reproduce? Most U.S. turtles lay their eggs from late spring to midsummer,
and many people have observed nesting turtles during the past few weeks.
These outdoor encounters have led to this and many other questions about
methods among turtles follow the basic format of most other vertebrates.
The mating season for most temperate zone species begins in late winter
or early spring as temperatures begin to rise. During this time, males
begin seeking females and engaging in courtship activities. Turtle biologists
assume that all species have a ritualized courtship process that leads
to the mating event itself, but courting behavior in the wild has been
observed in very few turtles.
combat occurs most commonly in animal species in which males get larger
than females, which includes white-tailed deer, wild turkeys, and humans.
The same appears to be true for all species of turtles in which males
are larger, but evidence is anecdotal and fighting is not well documented.
In snapping turtles as well as some species of tortoises, adult males
will engage in physical combat with other males. The purpose of such behavior
in turtles as well as other animal species is for a male to become dominant
by driving other males away from its territory, therefore preventing them
from an opportunity to mate with local females. Male tortoises of some
species will charge one another head-on and butt their shells together.
The loser is the one that eventually retreats or, in rare instances, is
turned over on its back. Snapping turtle males have been reported to fight
in the water, creating turmoil on the surface of a lake or pond as they
claw and bite each other. Observers of snapping turtle combat differ in
their interpretations of the details of the process, but in larger bodies
of water the loser usually retreats to another area and may even migrate
to another lake or stream. In turtle species in which the males are smaller
than the females, aggressive male-to-male behavior does not commonly occur.
have observed complex and intriguing courtship rituals in some species
of turtles. Adult male painted turtles, slider turtles (which include
the common red-eared sliders that are kept as pets), and some map turtles
have elongated foreclaws that are used in an elaborate courtship behavior
called "titillation." During this fascinating ritual, the male
turtle extends his front feet and turns them so that the backs are touching.
Then he vibrates his long claws in the water in front of the female. A
female interested in mating will follow the male, who slowly swims backward.
Other courtship rituals undoubtedly occur in various species of aquatic
turtles, but the chances are slim that someone will observe a short-term
event that occurs underwater for (at most) a few days once a year. One
of the best opportunities to see the titillation behavior is at a public
aquarium in which freshwater turtles can be observed through glass in
natural underwater settings.
by most or all turtles occurs by the male climbing on the back of the
female and curling his tail under hers. Male turtles of most species have
noticeably longer tails than females. A general rule is that the male
of turtles that mate on land has an indented area on the lower shell so
that he is not balancing precariously on her domed upper shell. Such indentations
are evident in many male tortoises and box turtles. Most aquatic turtles
that mate in the water, including sea turtles, have mostly flat lower
shells, as the buoyancy provided by the water allows the male to maintain
his position during mating. The actual mating process may last for several
hours in some terrestrial box turtles and tortoises.
during turtle nesting season I receive dozens of questions about the reproduction
process for turtles. This year was no exception. I have been asked numerous
questions during the past few weeks. I will answer some of them, such
as whether all turtles lay eggs, in next week's column.
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