Gail, Garth or Gerta? Cataloguing the giraffes of the Serengeti
If you had visited the lion research house between 2008 and 2010, in addition to Fabio, the stuffed lion, the mantelpiece full of animal skulls, and the aquarium of incredibly hardy fish, you would have seen this photo of a male giraffe, which I taped to one of the bedroom doors:
For the last few years, I’ve tracked these quiet giants of the Serengeti woodlands, studying their population dynamics, the vegetation they eat, and their interactions with lions and people.
We can learn a lot by keeping track of individual giraffes. Luckily, it turns out that each giraffe is born with a unique set of coat markings that persist throughout life, like human fingerprints or lion whisker spots. So, each field season, I arrived in Serengeti stocked with the materials necessary to catalogue the many giraffes I would encounter: several hundred 5 x 8 index cards, ink cartridges for the printer, sharp scissors, and a good supply of glue sticks. My days in the field often went as follows. Morning and afternoon: meander through the woodlands locating and photographing giraffes. Evenings: work through the day’s photographs, identifying giraffes and making ID cards for any new individuals. For fun, I assigned a different first name to each individual. The female below is named Flopsy, for her deformed right ear:
Among Serengeti giraffes, which belong to the Masai subspecies, coat markings vary from blocky to highly stellate, or star-like. While the patterns do not change, the color of the markings can grow darker as giraffes age, particularly for males. The shape, color and arrangement of the coat markings are all useful for telling apart different individuals. Other traits are useful as well, such as tail length or ossicone size, shape and hairiness. (Ossicone is the name for the bony, skin-covered horns of a giraffe.) I’ve included some giraffe photos below so you can try your hand at giraffe pattern matching. See if you can match the individual on the top row with any of the individuals in the bottom two rows:
Sexing giraffes is usually easy, especially at close range or from photograph. Aside from the obvious, adult males can be distinguished from females by their larger size, skull ossification (the ossicones of males are larger and mature males acquire additional bony skull protrusions) and their more erect posture. Sexing young calves is a bit trickier. The genitals of male calves are small and calves aren’t always willing to pose for the camera.
Here is an example of a mature male giraffe with significant skull ossification:
By the end of my 2010 field season, I’d amassed a catalogue of almost 1,000 giraffes. (Identifying giraffes by eye can be a laborious and error-prone process but Doug Bolger and colleagues at Dartmouth University have now released Wild-ID, software that assists with giraffe pattern recognition.
We are hoping that we can use the plentiful giraffe images coming in from the camera trap study to maintain this giraffe database and to monitor the population. It turns out, though, that many of the camera trap images contain only giraffe legs, which are much harder to use for identification than flanks.