| Introduction |
| Many mammal and bird game species have gender-based regulations
that allow the harvest of specific sexes on designated days. For example, the
white-tailed deer season is open for taking only of males (bucks) with the exception of
designated “doe days” in which females may be taken. These regulations are
valuable tools in wildlife management and conservation. |
| At the time of inspection by regulatory authorities, game
carcasses often are rendered to a state in which sex is not grossly apparent. In the
Wildlife Forensic Field Manual (Adrian (ed.) 1992), the author provides an excellent
review of anatomical elements that assist with determining sex in a decapitated big game
carcass and various avian species. Let us review some gross photographs and diagrams
from the manual. |
| Sex Organs |
| Identification of the sex organs obviously would be the easiest
way to identify the sex of a carcass. The external organs usually are cut away in
the field dressing process. Internally, the uterus, oviducts, or ovaries may be
inadvertently left behind in the caudal abdomen. |
| Penile Ligament |
| In male artiodactylids (Order of even-toed mammals), portions of
the penile ligament may be left behind in the field dressed carcass. |
 |
Here you can see the investigator pointing out the remaining
portion of the penile ligament in a cervid.
You can imagine how this structure might
be left behind in when the carcass in field dressed.
(Photo credit: Wildlife
Forensic Manual 1992) |
|
| Pelvis |
| There are numerous points of comparison on the artiodactylid
pelvis to help determine sex. Investigators divide these points into five
areas. These characteristics vary between big game species and maturity and require
experience to reliably differentiate sexes. Investigators may maintain reference
sets of pelvises of known age and species to assist with field identification. |
 |
Area 1 - Suspensory tuberosities (present in male, absent in
female) / This structure serves for the attachment of the penile ligament.
Area 2 - Ischial arch (V-shaped in male, U-shaped in female) / see
below
Area 3 - Pubic arch (thicker in male)
Area 4 - Ventromedial border of acetabulum (thicker in males)
Area 5 - Position of the iliopectineal eminence (mature animals
only)
(Diagram credit: Wildlife Forensic Manual 1992) |
|
| Cervical Vertebra |
| The sex of several species of artiodactylids may be determined by
comparison of the cervical vertebra. To perform this technique, the soft tissue must
be removed from the vertebrae and a transverse incision made through the column.
Thus, this technique is more likely to be applied in the laboratory. |
 |
Females lack the accessory articular facets as seen
on the left in the diagram.
(Diagram credit: Wildlife Forensic Manual 1992) |
|
| Lower Legs |
| Numerous measurements may be taken of the bones in the distal
limbs of big game species to provide supportive information about the sex of an
animal. These measurements differentiate sex on the basis of males being larger than
females. Application of this data requires the use of regional standards. |
| Avian Species |
| Similar guidelines are described in the Wildlife Forensic Field
Manual (Adrian (ed.) 1992) for sex determination in field dressed waterfowl, pheasants,
and turkeys. We will not review every aspect, but let us cover some basics. |
| Syrinx |
| The syrinx is the vocal structure of avian species. This
structure may be left behind when the head is removed from a waterfowl carcass and can be
palpated by inserting a finger through the thoracic inlet. |
 |
The syrinx is a sexually dimorphic structure in waterfowl.
Under hormonal influence, the syrinx develops into a much larger structure in males.
You can imagine how this structure would palpate differently between sexes.
(Photo credit: Wildlife Forensic Manual 1992) |
|
| Skeletal Measurements |
| Various game species of birds have reference data compiled on size
ranges of skeletal structures in males and females. Normally, the males are larger
than females; however, significant overlap may occur. In mallard ducks, six
measurements are used, including two sternal parameters, one scapular, one coracoidal, one
pelvic, and one humeral (Adrian ed. 1992). |
 |
| This ruler is available from the Nebraska Game and Parks
Commission and used for measuring the sternums of Ring-necked pheasants for sex
determination. As with mallard duck parameters, overlap exists between hens and
roosters. |
|
| External Characteristics |
Sexually dimorphic differences in plumage color and secondary
sexual characteristics may aid investigators in determining sex based on partial carcass
evidence, such as a pile of feathers or skin.
In some species, such as mallard and
wood ducks, differences in plumage color are striking and can be differentiated easily
between sexes. Keys exist to help distinguish feathers of sexes from species that
initially may appear very similar. |
 |
This is an example of a feather key for Ring-necked pheasants
used to differentiate back feathers. (Photo credit: Wildlife Forensic Manual 1992) |
|
| Other species, such as turkeys, have pronounced secondary sex
characteristics, such as beards and enlarged spurs. |
| Analyzing Trace Evidence |
 |
|
In some cases, it may be necessary to determine sex from blood or
a butchered meat sample.
In big game species, hormone analyses may be run on meat
and blood samples to determine sex. These analyses are limited to animals that are
in rut (males with elevated circulating levels of testosterone) and females with high
circulating levels of progesterone (pregnant or having an active corpus luteum).
More recent genetic methods are available, such as PCR amplification of genes on sex
chromosomes. |
| Scavenger
vs. Predator >> |
|
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Veterinary Forensic Pathology | Determination of Sex 
