By Drew Stazesky (University of New Hampshire)
Hey everyone!
We’ve started our final week conducting research in the Chobe Enclave of northern Botswana, and I’ll give some brief updates before continuing onto the main subject of my first blog post…
We spent the first week and a half at an abandoned hunting camp in concession CH1 of the Chobe Enclave. We packed up and moved yesterday to our second and final campsite, which is located just outside a village called Parakarunga. We’re in a fenced off piece of potential agricultural land, but there are signs of elephants everywhere around our campsite (aka poop) and last night we heard them rumbling and trumpeting very close by.
Oh! I guess I should mention that while at our last campsite we took two day trips into two other nearby villages: Kachikau and Kavimba. In Kachikau we visited with an Environmental Club of the local secondary school, and in Kavimba we got the opportunity to watch and listen as the president of Botswana spoke and responded to comments from the community. Both of these experiences were very cool and very unique, and the group had tons of fun.
Our camp in the Chobe Enclave – tents huddled around the biggest acacia tree for shade!
Now unto the main subject of my blog (a subject I find interesting, since I am more of an animal person), a subject that is very pertinent to the research we are conducting out here in Botswana: how to correctly identify the sex of an animal.
This piece of information is not part of the MOMS (Management Oriented Monitoring System) wildlife monitoring system that is currently conducted throughout Botswana’s wildlife areas, but is a part of DADS (Demographic Abundance through Distance Sampling) wildlife monitoring system that Round River is in the process of implementing here. The information we collect on transects is the information required for DADS.
So what piece of information am I talking about? Well first I will give you a quick lesson on something known as sexual dimorphism, which is what enables us to differentiate between male and female of a species (the majority of the time). Sexual dimorphism is when the males and females of a species differ in various physical ways—including body size, coloration, and in some species the presence and/or absence of horns. According to Trevor Carnaby’s “Beat about the Bush”, “sexual dimorphism is generally a result of males having to develop various characteristics, mainly physical, in order to successfully compete for females.”
And so in conclusion, what this blog post is about how we determine the sex of several species that we’ve seen quite a lot of throughout this semester.
Impala (a male and two female)
Antelopes
Kudu (Tragelaphus strepsiceros) and impala (Aepyceros melampus) are good examples of two antelope species that we see frequently on transects. Males of both species possess horns (and to clarify, horns are not the same as antlers; antlers are regrown each year while horns grow continuously until the individual has reached maturity) whereas females of these species do not have horns. The horns of kudu grow more elaborate as the individual matures, with a full three “twists” as the final result. Impala’s horns spread out further and grow longer as the male matures.
And so when we see a group or herd of kudu or impala, we look for the presence of horns to help us determine the sex of the individuals.
Buffalo
African buffalo (also known as Cape buffalo, Syncerus caffer) have a reputation for being one of the most dangerous animals throughout Africa. Both the males and females of this species are dangerous, and both of them possess curved horns. The presence of horns on both sexes can complicate identifying the sex of individuals in a herd at first glance, but a closer look reveals a key difference.
Despite the fact that the bulls are generally more massive than the cows, the bulls also possess a “boss,” which is a “central horn perturbance” made of sclerotized keratin at the junction of the two horns. This “boss” provides extra cushion and protection when the bulls literally butt heads over the cows (females). The cows don’t possess a boss, and instead at the junction of their horns is a wider expanse of thick black-brown hair.
Giraffes
Giraffe (Giraffa camelopardis) has been one of the most numerous species we’ve seen out here in Chobe, so we’ve been getting a lot of practice at sexing individuals. There are a few ways to determine male from female, and some easier than others. One of the simplest ways to determine male from female is to look at the stomach of the individual and see if it has a “bellybutton.” Males are the only ones who possess this “bellybutton” (because it isn’t actually a bellybutton…).
Another more challenging way to differentiate between the sexes is to look at the horns (known as ossicles), which both males and female have. But in mature males, the black hairs located at the tops of the ossicles are rubbed off from fights with other males, exposing the bare bone underneath. Any remaining hair is tufty and sparse. Females tend to have a smooth and even covering of black hair on the tops of their ossicles.
Another, but not foolproof, way to differentiate is to look at the coloration of the individual. Mature males can be much darker in color as compared to paler females and juveniles.
Elephants
We’ve seen at least 200 elephants (Loxodonta africana), if not more, during this past month and a half since our arrival, and we’ve become better and more efficient at differentiating between the sexes. Elephants are one of the harder African mammals to correctly sex, but we aren’t deceived like so many others by the presences of tusks because we know that both males and females possess them.
Generally speaking males are larger and more bulkier than the females, but both genders grow throughout their lifetime and so size also can’t always be a determining factor.
One more accurate way to determine the gender of an individual is to look at the shape and slope of the forehead. Mature males (aged in their mid to late teens) have a rounded forehead compared to the females’ more angular and sharply angled profile.
It takes time to acquire the knack for determining the sex of an elephants, and overall we are still practicing. But there is one foolproof way that we’ve discovered to identify a male elephant, and that is to look for the presence of a “fifth leg”…something the females won’t possess. This is very similar to looking for the “bellybutton” on a giraffe.
Zebra
There are plenty of zebra (Equus burchelli) around our current campsite, and it even looks like we have our own resident herd that grazes in the grassland just down the hill from our tents every morning. And so, over the next week I expect that the group will get more familiar with determining the sex of individuals in a herd.
Differentiating between the two sexes can be very difficult because zebras don’t possess any physical differences between the two sexes: no horns, no color differences and no pronounced difference in size (although the males—stallions—do tend to possess thicker necks). So basically there’s no external way to determine the sex of an individual, and so one of the only known ways is to get a good look at the butt. Females (mares) possess a thick black band/stripe between the rear legs underneath the tail (some of us fondly refer to this as the “thigh gap”), whereas the stallions only have a thin black stripe in the same place. It helps when the flies are out and the tails are swishing constantly and exposing that crucial area!
Birds
Now determining the sex of individual birds can sometimes be as easy as seeing which of the pair is the most colorful—as with the bright red breast of the male scarlet-chested sunbird (Chalcomitra senegalensis) as compared to the drab brown of the female. But then with some bird species there is no obvious coloration difference, and it could be determined by bill/beak size (i.e. the males might have the bigger bills).
One bird species that we have all become proficient at determining the sex of is the bataleur, or short-tailed eagle (Terathopius ecaudatus, a bird on our “birds of concern”). When an individual flies overhead, we simply have to look up at the underwings and see if there is a thick black peripheral wing stripe (male) or if it is a slender black peripheral wing stripe (indicating a female, and this thin stripe we fondly refer to as the “g-string”).
And then there are some species for which we have no hopes of differentiating between the sexes with only our binoculars.
And so, as the middle of the semester approaches and data collection continues, determining the sex of individuals will remain prominent in our daily lives here and each of us will continue to hone our skills.
For those back home who found this blog interesting (maybe even inspiring?) you are now equipped with some basic knowledge on sexual dimorphism and some ways to differentiate between the sexes, so go ahead and get outside. Observe the natural world around you and test your skills at determining the sex of the animals and birds you see around you!
(P.S. Happy Halloween!)