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June 13, 2011

Celebrating the 30th Anniversary of the Black-Footed Ferret’s Rediscovery - Part IV: Beginning of Breeding Season

Due to the Black-Footed Ferrets (BFFs) having a small founding population, it is important to maintain genetic diversity as much as possible. In order to do this, BFFs must be moved between breeding facilities so we are not repeatedly breeding the same pairs of ferrets year after year. The BFF Species Survival Plan (SSP) has a genetic advisor and studbook keeper, both use a computer program to decide what animals should be paired. Once these recommendations are made, the animals are transferred as needed. In order to reduce stress, we try to do as few transfers as possible. It also seems that some animals have better production if they are able to stay at the original facility they were raised at. However, we must do transfers to benefit the species in the long run. Most BFFs settle down fairly quickly due to all the breeding facilities having a similar setup and routine.

The lighting in the BFF room is a crucial factor for breeding success. The intensity is measured in foot-candles at each enclosure. Day length is also changed according to the time of year. Being from the Great Plains, their lighting needs are similar to our natural light cycle here in Colorado. However, we do adjust it each month going from 8 hours of light from Oct-Dec and increasing one hour each month until May. The increasing day length signals the BFFs to prepare for breeding season.

Male BFFs begin to show breeding readiness slightly earlier than the females. In late December, the testes start to enlarge and sperm production kicks into full gear. They are checked weekly for signs that they are coming into season. This is to ensure that they have sperm ready for when the females come into season later on. As a result of the genetic bottle neck, the sperm quantity and quality is decreased from what normal animals had in the wild prior to the bottleneck. In order to optimize breeding success, we conduct sperm concentration counts to make sure the males are at their prime breeding readiness. The males BFFs are anesthetized for the procedure and semen is collected. The samples that are collected are then loaded into a hemocytometer for counting under the microscope.

a) On each side of the hemocytometer is a square grid that contains 9 squares.

b) Only the 4 outside corners are counted, but on each side of the hemocytometer.

c) There is an even smaller grid within the grid on each side. In each corner, there
are 16 squares.

d) Each square is looked at and the sperm are counted in each of the 64 squares with
the average taken between the two sides. That number is then placed into an
equation to get the total concentration for the volume of semen collected.

Our goal is for the male to have above 250 million sperm per milliliter of semen. If the male is above the goal, then he can be used for breeding. If he is under, then he can be given a few more weeks and tested again. However, if the male is needed for a pairing before he is ready then he will be used if there are no other males available.