Foot-drumming Among Kangaroo Rats and Other Mammals

This paper was written as a way to summarize information on kangaroo rats and their foot-drumming. I wrote it prior to conducting a research project along with Dr. Charly Easterling, where we analyzed recordings of foot-drumming from giant kangaroo rats (Dipodomys ingens). Writing this literature review helped narrow down what we wanted to focus on during the research, making it an essential part of the scientific process. I hope that you enjoy reading it and learning interesting facts about these creatures!

by Michael Borden

 

 

 

 

 

 

Foot-drumming Among Kangaroo Rats and Other Mammals 

Michael Borden 

October 3, 2023 

Dr. Charly Easterling 

Research Topics 

 

Forms of Animal Communication 

The animal kingdom has a wide variety of communication styles and purposes. Many mammals, birds, and humans communicate via vocalization or through the usage of vocal cords to create sounds. Humans are unique among these in that they have different languages, which allows for more accurate communication of ideas and thoughts. Other animals will use sound in different ways, such as snakes hissing or cicadas buzzing. Another type of communication, vibrational, is a form of communication that travels through a surface, such as the ground, as opposed to the air, as most sound waves do (Hill, 2001). This is less common than other forms of communication and is often used among insect colonies or burrowing mammals. One type of species that primarily uses this type of communication is kangaroo rats, especially in their foot-drumming techniques. This paper will primarily be focused on kangaroo rats and their methods of communication, with other examples used as relevant. 

Besides different forms of communication, there’s also a variation in why and with whom animals communicate. Much communication is done within species as a means of operating more efficiently (as with insect colonies), of finding a mate, or marking territory. Without this communication, most species would not be able to survive and thrive as well as they do. Furthermore, warning and anti-predator signals are common, which kangaroo rats primarily do through foot-drumming (Randall et al., 1995). Contrary to the primarily intra-species communication of ​animals, however, these anti-predator signals are often communicated between different species as a warning or deterrent. They also can help protect a community, but in a more direct way than the others. Therefore, we can see that there are different methods and meanings for communication between animals, all of which are essential to survival of both the individual and species as a whole. 

Reasons for Vibrational Communication 

As mentioned earlier, vibrational forms of communication are unique in that they are focused more on travelling across surfaces rather than through the air or visually. This form is rare among humans, as our bodies aren’t primarily designed to pick up on or create minute changes in vibrations. However, there are multiple examples of this among the animal kingdom. Burrowing rodents will use vibrations to “see” underground and forage for food (Narins et al., 1997). Other sizable mammals can use vibrations to detect weather and earthquakes or for “talking” to each other (O’Connell-Rodwell et al., 2001). Additionally, many insects or smaller invertebrates use vibrational communication, as most are unable to vocalize. ​​Thus, there is no shortage of creatures that use this unfamiliar type of communication.  

Studies done on multiple species have shown that vibrational patterns are species-specific, meaning each one has a unique signal, even when they live far apart (Hrouzkova et al., 2018). This can help reduce inter-species competition, as “listening in” on another species’ signal is difficult or impossible. It’s unclear so far as to whether there’s a pattern to the differences, although in most spalacids, which are large rodents like mole-rats, there was a correlation with the distance between pulses and body mass. These species-specific signals are especially found in kangaroo rats, of which there are many different species, each with their own unique way of foot-drumming. There seems to be a correlation with size in these species as well, with the larger kangaroo rats having more complex patterns. Thus, these types of signals could be a good way to tell similar species apart, after close study has been conducted. 

Common among kangaroo rats is their foot drumming response to predators (often snakes), which serves multiple purposes. First, it dissuades the predators by warning them that they have been detected. This drumming pattern is usually done within the rat’s burrow if an animal is too large to come in, and outside if the animal can enter the burrow or is already inside. A study on great gerbils found they do the same thing, staying inside the burrow when dogs or humans are around but going outside when snakes ​are inside the burrow (Randall et al., 2001). These studies demonstrate that anti-predator responses can change depending on the type of predator that has been detected. Another use of foot drumming is as a warning to other members of the same species. For instance, the great gerbils’ drumming was mainly directed towards young of the species to protect them and to warn other individuals of the same species. This behavior is less common among kangaroo rats, however, who mainly foot-drum so a predator knows that it has been detected. 

Kangaroo rats are also good at measuring the danger levels of predators. In a study by Randall & Stevens in 1987, kangaroo rats were able to differentiate between a live snake and an inflatable one, giving slightly different responses to each. Their main behavior towards snakes involves foot-roll drumming, as well as kicking sand and jumping back at snakes, consequently making them less likely to attack. One study found that with this behavior, snakes wouldn’t strike at kangaroo rats at all, whereas they often would (85% of encounters) if this behavior wasn’t exhibited (Whitford et al., 2017). Even in the scenarios where a snake did strike, the kangaroo rat was never killed or seriously injured due to them jumping away or kicking at the snake’s head. After most of these strikes, rats would stay in the area and exhibit more anti-predator behavior to deter further attacks. Thus, we see that kangaroo rats are well-equipped to deter and protect themselves against predators.

Vibrational Communication Among Kangaroo Rats 

Foot-drumming and other vibrational communications can be measured in multiple ways, helping us understand how each species uses it uniquely; this could also potentially be a way of distinguishing similar species from each other. The pulse patterns can be measured through the number of pulses in bouts of drumming, the time between each pulse, and the time between each bout. One could also measure the change in the speed of drumming, the volume, or the frequencies involved (Schuppe et al., 2021). 

One recent study related to kangaroo rat drumming was on whether they respond to car traffic with anti-predator responses (Johnson et al., [Unpublished manuscript]). The kangaroo rats didn’t respond at all to traffic in a natural habitat and barely responded to scratching at the burrow entrance. This result could have been because of the time the study was done or whether a burrow was unoccupied. Another study found that ​Stephen’s kangaroo rats (Dipodomys stephensi) that were placed in arenas would respond to traffic with foot-drumming (Shier et al., 2012). Considering these two studies together implies that there could be a difference in responses between a natural and artificial environment. The rats that did react to vehicle noise also did the same after hearing a foot-drumming recording, showing that this may not have been merely a predator response. 

Many animals that utilize vibrational communication are specially adapted to do so. For instance, woodpeckers’ beaks have adapted to be incredibly strong for them to do their intense drumming on trees (Schuppe et al., 2021). Likewise, kangaroo rats possess strong feet that allow them to foot-drum regularly. Besides the part of the body that produces noise, many animals that communicate vibrationally will also have specially adapted auditory sensors that allow them to hear the vibrations. Considering that higher frequencies don’t travel as well through dirt, most burrowing mammals, such as kangaroo rats, are able to hear

frequencies that are lower than most other animals are able to (Webster, 1966). For instance, kangaroo rats that foot-drum emit more otoacoustic frequencies, which allow for greater hearing sensitivity among lower frequencies, than non-foot-drumming species do (Shaffer & Long, 2004). 

Further Studies 

The realm of vibrational communication in animals has been studied far less than that of open-air signals (Hill, 2001). ​This leaves many options for further studies and experimentation in this field. An example of potential studies that have little research is the changes in communicational behavior at different times or seasons. Another instance is how changes in light pollution might affect animal behavior in cities. A different rarely studied field is that of human impact or interference on animals that communicate through vibrations. This anthropogenic influence can have a larger effect on the environment than we realize, including animals’ behaviors (Berger-Tal et al., 2011). Thus, studying the impact this has would allow us to better expand our viewpoint of conservation ecology. Regarding kangaroo rats specifically, many more studies could also be conducted. The study mentioned earlier about giant kangaroo rat responses to traffic could be just the beginning in understanding human impact on this endangered species. Understanding more about our impact, especially harmful behaviors, can help to protect and preserve them better.​ While these topics may not seem incredibly important to us, they may allow for a greater understanding and insight into this lesser-known type of animal.  

References 

Berger-Tal, O., Polak, T., Oron, A., Lubin, Y., Kotler, B. P., & Saltz, D. (2011). Integrating animal behavior and conservation biology: a conceptual framework. Behavioral Ecology, 22(2), 236–239. https://doi.org/10.1093/beheco/arq224 

Hill, P. S. (2001). Vibration and animal communication: a review. American Zoologist, 41(5), 1135-1142.  

Hrouzková, E., Šklíba, J., Pleštilová, L., Hua, L., Meheretu, Y., Sillero-Zubiri, C., & Šumbera, R. (2018). Seismic communication in spalacids: signals in the giant root-rat and Gansu zokor. Hystrix, 29(2), 243.  

Johnson, A., Karels, T.J., Dunagan, S. P. & Steinkamp, E. (2023). Behavioral response of the endangered giant kangaroo rat (Dipodomys ingens) to vehicle vibrations (Manuscript Draft). Western North American Naturalist. 

Narins, P. M., Lewis, E. R., Jarvis, J. J., & O’Riain, J. (1997). The use of seismic signals by fossorial southern African mammals: a neuroethological gold mine. Brain Research Bulletin, 44(5), 641-646.  

O’Connell-Rodwell, C. E., Hart, L. A., & Arnason, B. T. (2001). Exploring the potential use of seismic waves as a communication channel by elephants and other large mammals. American Zoologist, 41(5), 1157–1170. https://doi.org/10.1093/icb/41.5.1157  

Randall, J. A., Hatch, S. M., & Hekkala, E. R. (1995). Inter-specific variation in anti-predator behavior in sympatric species of kangaroo rat. Behavioral Ecology and Sociobiology, 36, 243-250.  

Randall, J. A., Rogovin, K. A., & Shier, D. M. (2000). Antipredator behavior of a social desert rodent: footdrumming and alarm calling in the great gerbil, Rhombomys opiums. Behavioral Ecology and Sociobiology, 48(2), 110–118. https://doi.org/10.1007/s002650000199 

Randall, J. A., & Stevens, C. M. (1987). Footdrumming and other anti-predator responses in the bannertail kangaroo rat (Dipodomys spectabilis). Behavioral Ecology and Sociobiology, 20, 187-194.  

Schuppe, E. R., Rutter, A. R., Roberts, T. J., & Fuxjager, M. J. (2021). Evolutionary and biomechanical basis of drumming behavior in woodpeckers. Frontiers in Ecology and Evolution, 9, 649146.  

Shaffer, L. A., & Long, G. R. (2004). Low-frequency distortion product otoacoustic emissions in two species of kangaroo rats: implications for auditory sensitivity. Journal of Comparative Physiology A, 190, 55-60.  

Webster, D. B. (1966). Ear structure and function in modern mammals. American Zoologist, 6(3), 451-466.