Protocol for Assessing the Relative Effects of Environment and Genetics on Antler and Body Growth for a Long-lived Cervid

The overall goal of this experimental design is to assist whether population level genetics restrict white-tailed deer, odocoileus virginianus antler and body size by controlling for other variables that also influence antler and body size such as age and nutrition. This methodology can really help us understand the true cause of morphological variation in wildlife species across their range. And this is important because morphology is the basis for historical designation of sub-species and with Endangered Species Act codifying those sub-species differences it's important to understand are those differences really due to genetic differences that are meaningful and need to be preserved or are they just nutritional habitat quality differences that are associated with the habitat where those sub-species occur?

The main advantage of this technique is that it allows us in a controlled environment to focus on a specific characteristic of the environment that the animals were raised in naturally and in this case we're removing the animals from their natural habitat and controlling for nutrition to see if nutrition is the cause for the morphological differences. This technique can actually improve the implementation of the Endangered Species Act because it's gonna allow state resource agencies with limited resources to identify meaningful genetic variation. Demonstrating the technique today will be Dan Morina.

A graduate student here at the MSU Deer Lab. Begin by insuring that side fencing has shade cloth to act as a visual and physical barrier between pens. Install elevated box blinds at one end of each pen to facilitate darting events during data collection.

Keep two trough style feeders at separate ends of each pen to reduce competition for food among deer. Finally, provide deer with a high quality diet add Lupitum. Begin by walking the technician who'll be darting to the end of the pen where the elevated blinds are located.

Post a single technician into a blind. Then have the individual who walked the technician to the blind walk back to the opposite end of the pen. After confirming sedation of the deer by checking for eye reflexes apply ophthalmic ointment to the eyes.

And blindfold deer to reduce stress. Load the deer on a military-style gurney. Next use a rectal thermometer to assess body temperature after recovery.

Warm deer with heated blankets if the animals temperature is below 37.7 degrees Celsius. Or cool the deer with ice packs if the animal's temperature is above 40 degrees Celsius. And transport it via utility task vehicle to a predetermined data collection area.

Once transported, measure body mass to the nearest hundredth of a kilogram with a digital hanging scale. As well as hindfoot length and total body length to the nearest millimeter. Then administer size-appropriate amounts of antibiotic ivermectin, a custodial vaccine and a leptospirosis vaccine.

Next, while the animal is sedated take three antler measurements from adult males using an antler measuring tape. Measure the inside spread, basal circumference and the main beam length of antlers prior to antler removal. Then remove antlers about three centimeters above the burr using a reciprocating saw.

After the data is collected place the deer into the appropriate pen. And administer either 125 milligrams per kilogram of yohimbine hydrochloride or 4.0 milligrams per kilogram of tylosin hydrochloride to reverse the effects of xylazine hydrochloride. Finally, monitor the deer to ensure they remain in a sternal position until they come out of sedation and are fully alert.

After acquiring the antler samples measure each individual tine protruding from the main beam and additional abnormal points by aid of wire. Wrap the wire around where the tine intersects the main beam and mark that point for reference. Then measure from this reference point to the tip of the tine and repeat for each tine.

Next collect the remaining circumference measurements by identifying the smallest point between the G1 and G2 tines the G2 and G3 tines and the G3 and G4 tine if present. If the G4 tine is not present measure the distance between the mid-point of the G3 tine at the end of the main beam. And measure the H4 circumference at the midway point.

Finally, weigh antlers to the nearest tenth of a gram using a scientific digital scale. And design a minimal, critical antler mass of one gram for first year animals with antler shorter than three centimeters. Results from this study indicated that improved nutrition had a positive effect on all morphometric measurements on a 3.5 year old male white-tailed deer from each source region.

Antler mass and antler size did not vary among the three source regions after two generations of improved nutrition. Which suggest that antler size is not restricted by population level genetics. Further, body mass greatly increased from first to second generation.

Suggesting there is a nutritional limitation in the wild for all populations. However, there were still regional variation among second generation males. Once mastered, this technique only takes about an hour per animal.

But sample size is really important so you wanna have as many animals in your study as possible so you could end up spending several days if needed to process all of your animals. While attempting this procedure it's really important that everything within the deer pens is set up for success. The blind needs to be properly placed at the correct distance from the fence.

Shooting lanes need to be cut if there are branches in the way. And everything that you can control needs to be controlled in advance because the one thing you cannot control is how the animal will behave under the particular stressful situation you're putting them into. Using this procedure you could also modify the nutritional components of the experiment.

And look at how protein or energy intake might alter that genetic potential and the morphological expression of the animal. This same methodology can be used by other researchers to vary the type of treatment that's supplied to the animals and look at other things beside morphological development. You could look at how nutritional intake affects life history traits such as reproductive traits and recovery from the demand of gestation and lactation.

After watching this video you should have a good idea of how to control nutrition and age to see how genetics and nutrition interact in the morphological development of an animal within a captive facility. Don't forget that whenever you sedate a wild animal even in a captive facility there's a chance for injury to the animal so we have to take care and monitor them closely.