Sex at the Zoo
Air Date: Week of February 10, 1995
Host Steve Curwood takes a trip to the Franklin Park Zoo in Boston to talk with Dr. Donna Fernandez about sexual behavior in the animal kingdom. Hear what elks, crickets and seagulls have in common with the mating rituals of people. A Valentine's Day treat!
FERNANDES: These are alligators. It's a rather romantic call, loud and robust, but until I had done this program I really was not aware of the fact that there are mating calls in alligators.
CURWOOD: Sounds more like a Harley Davidson.
CURWOOD: Meet Donna Fernandes: zoologist, Vice President of Programming, and presenter of the yearly Valentine's Day Sex at the Zoo lecture at Boston's Franklin Park Zoo. Her shows are always a big hit. Standing-room only audiences fill a small amphitheater at the zoo's African Tropical Forest Pavilion again and again to hear what humans have in common with our feathered and furry friends when it comes to courtship and mating. A surprise from Dr. Fernandes: just about any human sexual behavior can be found in the wild kingdom. Take for example the mating call. The human male's street corner whistle has its counterpart in the vocalizations of male elk, parrots, even insects.
FERNANDES: This is a common field cricket. Probably most of you have heard this out there. What's neat about field crickets is the rate at which they call is related to their body temperature, and in fact one of the early scientists at the beginning of this century worked out the formula so that you could actually tell the temperature of the air by counting the number of chirps in 15 seconds, and I think adding the number 22 or something. I forget the exact formula, but you can find a clear relationship between chirp rate and temperature.
(Birds caw in the background)
CURWOOD: But it's not a thermometer; it's a love call.
FERNANDES: Yes, it is a love call. And so, females have to sort of take into consideration what the air temperature is when they are responding to a call. Because very often, species differ only in their calling rates. So a female not only has to listen to the call, but sort of adjust that to the outside temperature so she's sure that she's responding to the right male.
CURWOOD: Oh, this is very loud.
FERNANDES: The 17-year cicada. They're really interesting in that they take about 17 years to develop. After they sort of emerge from the ground, the males climb to the tops of trees and they emit this really loud buzzing call, and females then fly into where the males are and copulate with them.
CURWOOD: I guess if they've been waiting 17 years, they deserve it. Okay. And this?
CURWOOD: This sounds like rutting season to me.
FERNANDES: That's right. This is an elk call, and they also vocalize. And what's interesting about elk, is females often choose mates on the basis of their call in that they prefer to mate with males who give very long vocalizations, so that the bout length is quite pronounced. As well as the calling frequency, because there's quite an energetic demand to vocalize. And so, if they mate with animals that are able to call for a long time, amounts of time, it means they're in very good body condition.
(Elk call continues)
CURWOOD: Now, Dr. Fernandes, why study sex in animals?
FERNANDES: Well I've always thought it was very interesting to understand some of the complex, bizarre behaviors that you see. Courtship, even some of the characteristics that males have evolved which function solely to attract females, like elaborate plumages in peacocks, or inordinately large bright red breasts in frigate birds and things. And also, the duration of copulation can vary so much in species. How come some can get it over with in 3 seconds and others remain together in amplexis, if they're frogs, for 6 months? I mean, why stay on a female for 6 months? And so, I always thought that those kinds of questions were really fascinating.
CURWOOD: And what are some of the answers? Why 6 months?
FERNANDES: Well, animals that remain incopulate for a really long time, it's usually as a way of guarding the female or reducing the risks that some other male is going to come and fertilize her. So probably only a small portion of that time is actually needed for the transmission of sperm. Thereafter, it's mate-guarding.
CURWOOD: Now, with sexual reproduction as a way to mix up the genetic pool, and this behavior around sex, the courtship and duration stuff, is to do what? What's the biological purpose of that?
FERNANDES: Well, I think it really comes down to the fact that females represent a very limited resource, in that eggs are much, much larger than sperm. So females can only lay a limited number of eggs in their lifetime. Because females make these larger eggs and also often invest thereafter by carrying the young in a pregnancy, or lactating so they give breast milk, they're making this huge investment, whereas often males give little more than their sperm. They copulate with the female and they're gone. That sets up competition among males for access to those females, because there's certainly more sperm out there than there are eggs to fertilize. And it's that competition among males which has led to a lot of dominance, interaction, or the evolution of giant horns in males which they'll use to fight with each other. Or sometimes males can only get access to females if they bribe her with gifts. So there's sometimes courtship feeding, where males have to prove their worthiness by offering her some sort of dead insect if she's a hanging fly, and so females will copulate only if they get an insect prize. And the duration of copulation is related to the size of the prey, so that if you give her a really big insect she'll let you copulate with you for 25 minutes. If you give her a small little midge, you'll only get on her for 5 minutes. So those really interesting stories, I think, fascinate me.
CURWOOD: The presents of Valentine's Day have their precedents in nature.
FERNANDES: Oh, absolutely.
CURWOOD: So what species look for these presents? You mention these insects. Who else?
FERNANDES: Well, a lot of birds will insist on courtship feeding before they'll settle down with a male. And that's because in male birds, a lot of them do a substantial amount of parental care after the chicks are born. And so what you really want to evaluate is how good of a father is this male going to be. And so, if he's able to bring you lots of fish or lots of insects over a fairly short courtship period, then you know that once those babies are born, he'll be pretty good at going out and getting food for the offspring. So you're sort of assessing his parenting skills by how much he can bring you in a short period of time.
CURWOOD: So in general, in nature, the more attractive species are the males. They have the brighter plumage, the big peacock feathers or whatever. And the females are less attractive.
FERNANDES: Mm hm.
CURWOOD: So why the reversal for humans?
FERNANDES: Well, it's hard to say if that's true. If you looked at males and females without makeup, then I don't know if you necessarily would say that females are the more attractive. If you look at why makeup has sort of evolved in culture, very often it is to make you look younger, and to simulate sexual arousal. Rouge looks very much like flushed cheeks, or a lot of the eye makeup's supposed to make your eyes look bigger. But the biggest thing is you want to look young. Because in humans, and in a lot of animals, your value as a mate is dependent on youth. Because once you're slightly older, your reproductive potential is much less. You have fewer years ahead of you where you'll be able to bear children. And if you look at societies where there are multiple wives, very often males will have several wives and have very young wives. And even in today's society, very often successful men will divorce their wife when she's about menopausal or in her 40s, post-reproductive, and marry a much younger woman. And it's because he could have a much, a whole second set of offspring with another female.
CURWOOD: All right. Let's take a walk around the zoo and take a look at some of the animals.
CURWOOD: So we're in front of the chameleons here.
FERNANDES: Right. We have some panther chameleons. What's neat about these guys is, you can tell if a female's receptive by her body coloration. That if she's in a certain color state, she is receptive. And what's also neat about chameleons, and it's true of a lot of lizards and snakes, is they have 2 penises. Hemi-penes.
CURWOOD: Two penises?
FERNANDES: Right. And the one that they use depends on which side they approach the female. So if they approach her on the left side of her then they'll use their right penis, or if they approach her on the right side they'll use their left penis. So we've watched these guys copulate, and he doesn't seem to have a preference of which one he uses, but he does have 2.
CURWOOD: What do we have here? This is a marmoset, or...?
FERNANDES: It's actually a pado, which is one of the early types of primates called prosimian primates, and they're found deep in the forest canopy of West Africa. And what's interesting about these guys is they copulate upside down, which is -
CURWOOD: Upside down?
FERNANDES: Upside down, very interesting to watch. And also, that what the male will do is he uses a mating plug. So after he copulates with a female, he'll sort of seal up her genital tract by having a substance that's mixed in with the semen that has a glue-like property. And that helps, because it sort of seals her up; it's like a little chastity belt. It's going to limit when she can mate with another male, and usually it allows enough time for his own sperm to travel up her reproductive tract. And this is very common in a lot of insects as well, who will use these mating plugs. And in fact, there's this interesting type of worm called an ecanthocephalon worm, which also, when he mates with a female, he'll cement up her genital tract. Well they have a phenomenon known as homosexual rape in these ecanthocephalon worms, where males will copulate with other males only to seal up their genital pores, because it's in effect sterilizing rival males. So once they're all sealed up with cement, they can't copulate with other females. So you may be the only intact male in town if you've been able to take all these other males out of commission.
CURWOOD: What have you learned most about human sexual behavior from the animals?
FERNANDES: Well, probably that anything that you've ever seen in human sexual patterns, bizarre as it may seem, you can find examples in the animal kingdom.
CURWOOD: Okay, you walked into this. Give us an example.
FERNANDES: Well, this year's program for our annual Sex at the Zoo, I'm going to be talking about homosexuality, transvestism, and sex change in the animal kingdom. And, at first I thought homosexual behavior was rather rare in animals, because you really just don't see it that often. But I've been doing a lot of research on this and found that, in fact, you do find lots of cases where males will copulate with other males of their own species, or females will remain together and raise young together, so-called lesbian gulls. And transvestism is a very common phenomenon in animals where you will have males that will mimic the appearance and behaviors of females, and there are a couple of reasons why they might want to do that. Often, if you mimic a female, you'll be able to sneak into the territory of another male; he won't suspect that you're a male. So when that territorial male is off defending maybe the border of his territory, you can sneak copulations with all the females that are in his territory. Or when I talked about the insects that insist on getting a nuptial gift before they'll copulate, well there are some males who will adopt the sort of flight pattern and courtship pattern of females so that when males offer them the nuptial gift thinking that it's a female, they'll steal it. And then they'll go off and try to court a male with the stolen gift. So, you know, you might think that transvestism in humans is really a bizarre phenomenon, but there are cases in the animal world as well where males will take on the appearances of females for some reproductive gain.
CURWOOD: I want to thank you for taking this time with us. Dr. Donna Fernandes is Vice President of Programs and Curator of Research here at Boston's Franklin Park Zoo.
FERNANDES: It's been a real pleasure to talk with you today. Thank you very much.
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