During this episode, Bill breaks down the topic of reproductive delays, with a special focus on the American black bear (Ursus americanus). Come join the guys as they “peek inside the den”, and uncover this seldom-discussed aspect of the sex lives of some of our fascinating (and randy) mammals.
This episode takes place at the Hampton Brook Woods Wildlife Management Area in Hamburg, NY. It was recorded on January 19, 2020.
Episode Notes:
Bill did a poor job of explaining to Steve what “estrus” meant. Steve seemed to come away thinking that the word simply meant “mating”, and Bill didn’t notice this until he was editing the episode. Bill should’ve clarified that it means: a recurring period of sexual receptivity and fertility in many female mammals; heat. "a mare in estrus"
Questions that came up during the episode:
1. Is delayed implantation obligate?
Sometimes! It appears that, for what we were discussing in this episode, the answer is usually “yes.” Here’s a more thorough explanation: “Two types of mammalian embryonic diapause have been identified. Facultative diapause is also known as lactational delayed implantation due to its regulation via lactation. If a female copulates while still lactating for a previous litter, the suckling stimulus will cause the embryos to enter into diapause. This is known to occur in some rodents, insectivores, and marsupials. Obligate diapause is also known as seasonal delayed implantation and is a mechanism that allows mammals to time the birth of their offspring for favorable environmental conditions. This mechanism occurs as a regular part of the reproductive cycle in mammals such as armadillos, all species of pinniped, many mustelids, all ursids, one species of fruit bat, and the roe deer.” - Wikipedia
2. Where are Roe Deer found?
The Roe deer (Capreolus capreolus) lives throughout Asia Minor and Europe (but not in the islands of Sardinia and Corsica) Lebanon, Israel, Ireland and in the eastern edge of Eastern Europe. They favor forest steppe as well as small insular forests within croplands, as well as high-grass meadows that have some shrubs. They like cutovers and burns in forestlands and croplands for the purpose of revegetation. - Animalia.bio
3. Are sharks viviparous?
Answer: Most sharks are viviparous.
If you were to ask H.R. Giger to design a ravioli, you could expect it to look something like a shark egg
4. Do weird rods fly around caves?
Absolutely! (but not really) “In cryptozoology and ufology, "rods" (also known as "skyfish", "air rods", or "solar entities") are elongated visual artifacts appearing in photographic images and video recordings.” - Wikipedia
5. In lion prides – do the males choose their females or vice versa?
From the research we did online, we’re pretty sure that it’s the guys. The average pride consists of around 15 lions, including several adult females and up to four males and their cubs of both sexes. The male or males associated with the pride must defend their relationship with the pride from outside males who may attempt to usurp them. - Live Science and Wikipedia
6. How does cryptic choice function physiologically?
As we should’ve guessed, there’s a whole world of information within this one question. Biologists have uncovered more than we thought, but there’s still a lot that’s not understood. There’s definitely an episode about this waiting to be made! Head down the rabbit hole and find out all the ins and outs of female cryptic choice by clicking here.
Photo Credit: Black Bear Clint Turnage/FWS
Links:
Check out our episode on hi-BEAR-nation!
Links to bear researcher attack videos: “We thought this bear was out cold. We were mistaken” / “Outdoor hub: Grizzly Attacks Bear Researchers”
Sponsorship of this episode provided by Gumleaf Boots, USA
Free shipping offer code for Patreon supporters: TFG2019
As always, check out Always Wandering Art (Website and Etsy Shop), who usually provides the artwork for our episodes!
Work Cited:
Bridges, A.S., Vaughan, M.R. and Fox, J.A., 2011. American black bear estrus and parturition in the Alleghany Mountains of Virginia. Ursus, 22(1), pp.1-9.
Friebe, A., Evans, A.L., Arnemo, J.M., Blanc, S., Brunberg, S., Fleissner, G., Swenson, J.E. and Zedrosser, A., 2014. Factors affecting date of implantation, parturition, and den entry estimated from activity and body temperature in free-ranging brown bears. PLoS One, 9(7), p.e101410.
Himelright, B.M., Moore, J.M., Gonzales, R.L., Mendoza, A.V., Dye, P.S., Schuett, R.J., Durrant, B.S., Read, B.A. and Spady, T.J., 2014. Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus). Conservation physiology, 2(1).
Orr, T.J. and Zuk, M., 2014. Reproductive delays in mammals: an unexplored avenue for post‐copulatory sexual selection. Biological Reviews, 89(4), pp.889-912.
Robbins, C.T., Ben-David, M., Fortin, J.K. and Nelson, O.L., 2012. Maternal condition determines birth date and growth of newborn bear cubs. Journal of Mammalogy, 93(2), pp.540-546.