Fire, freezing, molestation by predators, and trampling by cattle or
native ungulates are only a few natural sources of injury to which box
turtles have always been exposed. Man's civilization in the Great
Plains, chiefly his automobile and other machines, have compounded the
total of environmental hazards. Automobiles now constitute a major
cause of death and serious injury to box turtles. Each year thousands
are struck on Kansas highways alone, not to mention the many
casualties resulting from mowing machines, combines, and other farm
machinery.
Although grass fires usually occur in early spring or late fall when
box turtles are underground, some turtles are surely killed by fires
and many are injured. In early April of 1955 the pasture at the Damm
Farm was burned. Similar burnings, I discovered, had occurred both
intentionally and accidently in past years at irregular intervals. No
deaths or injuries, attributable to fire were discovered in the course
of intensive field work in the spring and summer of 1955, when the new
grass was short and conditions for finding and marking box turtles
were ideal. Badly burned individuals, if any, may have secreted
themselves until their wounds had healed. In June, 1957, an adult
female, that had been burned severely, was taken from a small puddle
in a ravine on the Damm Farm. The soft parts of her body, excepting
her head and neck, were a nearly solid mass of smooth scar tissue, the
scales and rugosities of the skin being practically obliterated. The
tail was reduced to a mere knob surrounding the anus and dead, exposed
bone was visible on most of the dorsal part of the carapace. Possibly
this female was burned in the fire of 1955. Lack of injury to the head
and neck can probably be accounted for by the additional protection
afforded these parts by the folded forelegs when the turtle was
withdrawn in the shell.
Turtles that are smashed flat on the highway, of course, have no
chance of survival. Highway fatalities are usually the result either
of "direct hits," where the tire of a vehicle passes directly over the
turtle, or of repeated pummeling by subsequently passing vehicles. The
writer, while driving behind other cars that struck turtles or by
sitting beside roads, has observed numerous turtle casualties. Most
are struck a glancing blow by a tire and are propelled some distance
through the air or on the surface of the pavement, often to the side
of the road. Such a blow is usually sufficient to crack or chip the
shell, or at least to scuff away parts of the epidermal covering.
Turtles, so injured, usually survive.
Parts of the shell do not break away easily, even when several deep
cracks are present, and only a little bleeding occurs. A common injury
inflicted on the highway is the wrenching and subsequent dislocation
of the carapaco-plastral articulation. In such instances the
ligamentous tissue joining the two parts is torn extensively. Under
these circumstances the movable shell parts seem to act as a safety
device, giving way under pressure that would crack the shell of a
turtle with rigid, fixed buttresses. Dislocations of the
carapaco-plastral articulation that have healed are characterized by
abnormally heavy development of ligamentous tissue, which may
elaborate a horny, scutelike substance on its outer surface.
The extent to which serious injury incapacitates a turtle is not
known. Surely open wounds are susceptible to infection and to various
kinds of secondary injury; normal activity is probably interrupted by
a period of quiescence, at least in the period of initial healing.
An injured female had a hole, slightly more than one inch in diameter,
in the right side of the carapace at the level of the second lateral
lamina. A tight, thin membrane stretched between the broken edges of
the opening; this membrane contained no bone and was covered
externally by scar tissue. It was obvious that this turtle had
recovered, at least in part, from a serious injury (inflicted probably
by a piece of heavy farm machinery).
Minor chips, scratches, and abrasions on the shell result from a
variety of sources, some of them mentioned above. Small rounded pits
in the bony shell (shell pitting) due to causes other than mechanical
injury, are found in nearly all kinds of turtles according to
Carpenter (1956), Hunt (1957), and my personal observation. In _T.
ornata_, however, the condition is less common than in the specimens
of _T. carolina_ described by Carpenter and in the remaining species
of _Terrapene_ that I have examined.
Carpenter (1956:86) came to no conclusion as to the cause of shell
pitting in _Terrapene carolina_ but suggested that a variety of
factors including parasitic fungi, parasitic invertebrates, and simple
shell erosion, might be responsible.
According to my own observations on turtles in the University of
Kansas collections, shell pits range in size and shape from shallow,
barely discernible depressions to deep borings; I suspect that shell
pitting for turtles in general has many causes, some of which may be
of more frequent occurrence in one species than in another.
Hunt (1957:20) presumably was referring to shell pitting by a more
suitable name when he wrote of, "... necrosis ... of mycotic origin."
Hunt (_loc. cit._) stated that "Of those cases which have been
recently examined, the author found all were due to the invasion of
Mucorales beneath the plates of the epidermal laminae. This disease is
of extremely common occurrence and has been found in all members of
the order but is seldom found in marine species. Mycosis more
frequently occurs on the plastron than on the carapace." Hunt
presented no evidence to support his statement regarding invasion of
the shell by Mucorales.
Evidence that injury to the soft parts of the body is also fairly
common is seen in the many _T. ornata_ with missing feet and legs.
Stumps resulting from amputations are covered with tough, calloused
skin and sometimes by horny tissue similar to that of the antebrachial
scales. Amputees are incapacitated only slightly in normal locomotion
if a functional stump remains; probably a cripple is somewhat
handicapped in other functions, such as burrowing, nest digging
(females), and copulation (males). Causes of amputation are discussed
in the section on predators.
Fractures of the limb bones are common. A female from Stafford County,
Kansas (Pl. 29, Fig. 4), showed a typical case of fracture and
subsequent repair; the right fibula had been broken and the ends
dislocated; a great mass of bone joined the repaired break to the
middle of the tibia, giving the entire skeleton of the leg the
appearance of the letter "H." The fibula, shortened by the
dislocation, no longer articulated by its proximal end with the femur;
the tibia probably bore the entire load in the period of repair and
the transverse connection that formed between the bones later took
over the function of the fibula.
There is little doubt that ornate box turtles are stepped on or
trampled by cattle, at least occasionally, but I never observed such
an incident; the predilection of ornate turtles for dung insects and
for moving along cattle pathways brings them to close quarters with
cattle and probably did likewise with native ungulates. A steer,
stepping on a box turtle, could inflict superficial damage to the
shell or cause broken limbs but would probably not crush the turtle
unless on a hard substrate.