TO BITE AND NOT BE BITTEN: THE CHALLENGE OF THE CAIMAN-EATING JAGUARS

Mysteries still remain around the killing bite of the sabertooths, although it seems clear that they relied on a combination of a huge gape and a surgically precise cut through the softer parts of their prey (such as the throat) to achieve a rapid death through blood loss. Modern big cats on the other hand use a different technique, applying strong and prolonged pressure with their short and robust canines, either suffocating their prey or crushing vital parts.

Among the pantherine cats, it is difficult to imagine a killing bite more different from that of sabertooths than the one employed by jaguars in South America to hunt caimans. What sort of anatomical adaptations allow the jaguar to deliver a bite devastating enough to kill a creature that boasts one of the most formidable armours in nature? In a recent assignment from National Geographic Magazine we set to explore precisely that subject, and how to reflect it in images.

Research into the anatomy of the skull of pantherines by several specialists has shown that the skull of the jaguar is adapted for generating larger bite forces than other big cats, due to slightly increased jaw leverage and to the larger cross-sectional area of the masticatory mucles, especially the temporal and masseter. But the differences with other species of the genus Panthera are subtle and there is also a behavioural factor, a preference (either genetically programmed or learned, or both) by the jaguars to go for a skull bite where other big cats would aim at the prey’s neck. When the chosen prey is a large caiman, as often is the case among jaguars from Brazil’s Pantanal, the efficiency of the skull bite is simply astounding. As the jaguar usually surprises the caiman from above and behind, the skull or nape bite is simply the best way to bite and not be bitten by a prey that can revolve and snap its deadly jaws with lightning speed.

Jaguars in the Pantanal spend lots of time patrolling the water margins in search of such prey as capibara or caimans. Photo courtesy of Luke Hunter/Panthera

Caimans are an important part of the Pantanal jaguars’ diet, wether they actively hunt them or scavenge them as in the case of this picture. Photo courtesy of Rafael Hoogesteijn/Panthera

For the National Geographic illustration, art editor Mónica Serrano proposed to work in layers so that we would have freedom to decide what parts of the anatomy of both predator and prey to show.
After all, the killing bite is an interaction between the geometries of both animals and the jaguar needs to allign its head and jaws in a very concrete position in order to penetrate the caiman´s superb armour. This interaction is so compex that there is no hope to show all the relevant factors in one single, 2-dimensional image.

My first pencil sketch, based in a draft sent early on by Mónica, shows the jaguar´s head in near-frontal view, which is the only way for us to show the relevant features of the caiman’s head and neck in a recognisable way

By choosing a frontal view we lost the opportunity to show clearly one important aspect of the jaguar’s killing bite: gape!

Although the gape of modern cats is small compared to that of the sabertooths, they are still capable of opening their jaws to an impressive degree as shown in this picture. Such gapes are neccesary if the jaguar has to encompass the head of a large caiman between the tips of its canines. Photo courtesy of Luke Hunter/Panthera

Once we established the angle of view, I proceeded to draw the anatomy of both animals from the inside out. This is an excercise I am pretty familiar with from my reconstruction work, but in this case I have the advantage of working from images of dissections and CT scans of the real animals, rather than having to infer the development of muscles from their attachment areas in the bone only.

I started by drawing the skulls of caiman and jaguar in a position corresponding to the killing bite

In the next layer I put the muscles in place. In jaguars, the great width of the area encompassed by the zygomatic arches, known as the temporal fossa, is a clear sign of the huge development of its temporalis muscle

In the final layer, I show the external appearance of the animals, with the armour of the caiman much in evidence

At this point in the process there was still an important task ahead: to select what sections of the deeper layers to show through. That was up to Mónica and her team, who produced the published image as we see it here

Using transparency and additional outlining it was possible to show the position of the jaguar’s mastication muscles, the caiman´s neck vertebrae and even its tiny brain.

In this video you can see the whole sequence of images, from the early pencil sketches to the layers of the colour illustration, and you can appreciate the difficult choices about what to show and what to hide.

See the National Geographic article on jaguars as published in the December issue of the magazine in this link:
https://www.nationalgeographic.com/magazine/2017/12/shrinking-kingdom-of-the-jaguar/

All artwork by Mauricio Antón, ©National Geographic