A New Image of Forest Elephants
Thermal imaging (also called “thermography”) has given us a new window into the social behavior of forest elephants. Of course the potential of scientific insights motivated our research (see links in sidebar), but the incredible beauty of the images was a treat in itself!
The color scale in the image at right ranges from 27.1-37 degrees Centigrade (dark blue to white), graphically painting the temperature of this elephant’s skin at 10 pm in the evening. Notice that even the warmest parts of his skin are several degrees cooler than the normal core body temperature of 37 C. This makes sense because the skin is used for thermoregulation and is usually cooler than the body core (touch your own skin and see that it tends to feel cool).
With information on ambient temperature and humidity, this thermal camera can be calibrated quite exactly and integrates the distance to the subject into the color scale. Many people wonder why there is a reflection in the pool. The explanation is that thermal energy is one part of the electro-magnetic spectrum that describes light. The surface of the pool is very cool and reflects this thermal “light”—but notice that the reflection is cooler than the actual elephant’s body! This is because the water absorbs some of the thermal energy and reflects back cooler radiation.
What is really “cool” is that we might be able to use some of this information to assess the health of an individual and in some cases we can see indicators of reproductive condition. For example, a pregnant female with no nursing calves will have noticeably hotter breasts than a female who is nulliparous (has never had a calf) because the tissues in her breasts are metabolically active preparing for lactation.
Pigs Go Bump in the Night
In the pitch black of night an infant male tests his courage against a sounder of red river forest hogs (Potamochoerus porcus) rooting for seeds in the piles of elephant dung that dot the forest clearing. His mom is drinking mineral water from the pool at the upper left and repeatedly the young male gets a bit scared and runs back toward the security of his mother. Neither the infant nor the pigs can see one another (the pigs don’t seem to care!).
The Valentine Saga
Valentine was born on 15 February 2012. This was only the second time that a forest elephant birth has been observed. At the beginning of this thermal video, captured at 8:30 pm, 4-hour old Valentine is stuck in a hole. His older brother and sister eventually help him climb out. Three hours later the family is near the edge of the forest and Valentine’s mother is hot (bright yellow) from being chased around by a young bull. Valentine has not been able to nurse even once since his birth because his mom is nervous from the young bull’s advances. But when his mom leaves him at the base of the tree, Valentine’s older siblings watch over him.
Amazing Thermal Elephants
Not only are these thermal images beautiful, but the detail of venation in the ears and the differences in skin temperature among individuals is striking. Notice the areas where blood vessels are near the skin surface to facilitate heat exchange (called “thermal windows”). These show up as much warmer patches of color on the body surface (areas that are brighter yellow). During the closeup video, notice how the calf’s ears are completely black while his mother’s are bright and you can see all of the veins. This is because the calf, with a smaller body, is not trying to loose heat any more and the veins in his ears are constricted and not visible.