Charles Darwin taught us about evolution and natural selection. Only the strong survive, competition is a way of life, he said. Making changes in a way of life in order to cope with competition is one way to survive in nature. The word adapt is defined as becoming adjusted to new conditions, adapting can involve a physical or physiological change throughout generations. The word acclimate is defined as a change in behavior to cope with a single environmental factor. In nature, adapting and acclimating to competition and the new lifestyle it brings is the only way to survive. The North American river otter, Luntra canadensis, is one such species faced with the task of adapting and acclimating to new changes in their environment. The common raccoon, Procyon lotor, is known as the catalyst of the river otters struggles. The littoral zone of lakes, rivers, streams and estuaries can be known as the environment where survival has become essential for both of these species. For the North American river otter the task of adapting and acclimating to this new challenge with which they are faced has become essential for their species survival. The river otter is already armed with an arsenal of tricks that have helped them become a thriving species they have been in the past, but with each day comes a new threat. If the river otter cannot complete this task, they face lower survival rates, lower population densities and eventual extinction. The adaptations and acclamations of the North American River otter could be the difference between survival or extinction.
The common raccoon and the river otter may seem to have nothing in common. Yet, they are brought together by one very important aspect, the littoral zone. This zone can be described as the shallow water making up the banks of lakes, rivers, streams and estuaries. The littoral zone provides a habitat for the prey of both the raccoon and the otter. With its rich moist soil, high nutrient contents, proximity to deep water and abundant vegetation for shelter, the littoral zone is the perfect habitat for frogs, small fish, numerous species of insects and amphibians (Gessner, 1999). This zone alone is a thriving ecosystem complete with its own food web, energy flows, nutrient cycles and even keystone species. This zone provides the otters with nesting places, as well as easy hunting areas that are close to the safety of the water and their burrow, but this is also a place favored by raccoons. With a dense number of trees, this zone provides the perfect shelter and protection for the raccoon. Raccoons hunt at night therefore need a safe place to stay during the day, the littoral zone provides that safe place. The littoral zones provide not only good hunting grounds and protection, but also the perfect place for the raccoons’ dousing ritual. With characteristics like high nutrients, multitudes of prey species and plenty of water, it is understandable that the littoral zone would attract numerous predators into the same area. Along with numerous predators comes numerous complications including competition and food scarcity. The river otter must learn to acclimate themselves to these changes in order to survive.
The North American River Otter, Luntra canadensis, is a nimble little creature found in waterways of the United States and Canada (Newmark, 2002). As agile on land as they are in water, river otters make their homes in the littoral zones of streams, lakes and rivers. Using the land as a burrow, otters are able to create a complex system of tunnels and nests all underground. Some otters have even built access to water from their underground home in order to avoid being spotted by their land-only predators (Ried et. al., 1994). Utilizing both land and water river otters are constantly on the hunt for food. Fish, frogs, crayfish, mollusks, some plants, invertebrates and other small mammals contribute to the river otters’ diet (Hansen, 2008). The prey available to the otter changes depending on the time of year. Certain food is not present in the otter habitat during the winter or during the summer therefore otters have learned to adapt diet accordingly. Depending on the temperature, precipitation and even pollution level of the water, otters will hunt for the most available, and easily catchable food source around them (Crait Jr. 2008). The otters ability to adapt does not stop at food. When their habitat is severely threatened, be it predator or human caused, otters must find other places to live. The ability to adapt to a variety of different habitats including coastal and inland areas allows for the otters to have a preference when it comes to their living environment (Maxfield et. al. 2005). The ability to change food and home preference, keep warm in the winter and cool in the summer, and stay safe from predators demonstrates the North American River Otter’s capacity to adapt to seemingly any change nature throws its’ way.
In the littoral zone, the river otter has almost always been the top predator in the water. On land otters only fear coyotes, mountain lions and possibly domestic dogs and cats (Hansen, 2008). Food is normally plentiful and threats are normally low. However, the common raccoon has become a threat to the river otters peaceful life. With the same tastes in food and shelter raccoons are quickly becoming accustom to the river otters’ niche. With limited resources like food the raccoon and the otter could be struggling to satisfy both of their similar needs.
The common raccoon, Procyon lotor, is a medium sized mammal that can be found almost anywhere. A patch of woods, neighbors back yard, mountainous areas and littoral zones make up this animals home. Although they hold the status of a native species in North America, most raccoons are considered pests and are quickly being pushed out of their comfortable urban environments (Davis, 2008). Raccoons are considered omnivores, consuming a diet of plants, various invertebrates and small animals such as frogs and fish (Davis, 2008). Due to their aggressive nature, raccoons do not tolerate much competition when it comes to finding food. Armed with sharp teeth and claws raccoons are prepared to fight any competition that comes its way. Finding food is the raccoons number one priority though. Raccoons have many adaptations for completing this task. The forepaws of a raccoon are lined with millions of sensitive nerves that allow them to search and feel for food, and also tell the difference between what is food and what is not (Zeleoff, 1988). Raccoons have often been spotted along the banks of streams and rivers “washing’ their food in the water. This action is known as dousing, and actually has nothing to do with the cleanliness of the food item (Zeleoff, 1988). The exact reason for dousing is unknown, but some believe the raccoons brain is so wired for this forage motion of picking up and putting down items, that the raccoon performs it subconsciously even when they have food in their paws (Zeleoff, 1988). Whatever the reason for this action, it brings the raccoon to the littoral zone of lakes and streams. The presence of raccoons in the littoral zone provides yet another dilemma for the river otter. In any environment resources are limited. The littoral zone is not different. There is limited prey, limited shelter and limited space. All these limits are bound to create competition; competition for food, shelter and space.
Not only does the presence of the common raccoon in the littoral zone cause the threat of competition for the otters, but it also generates other concerns. The safety of the otters nest, lower levels of food availability, higher threats of disease and even the threat of physical harm is present for the otter. Raccoons have an excellent sense of smell (Zeveloff,1988). With this, they could easily smell the otters den and invade, killing the otters young and endangering the adults. This constant invasion of otter nests could wreck havoc on otter populations. With a gestation period of about 11 months, female otters only give
birth once a year, they then spend up to 6 months raising the young (Melquist, Hornocker, 1981). If a females nest is invaded by a raccoon it could possibly be an entire year before she mates again causing a huge set back in the areas otter population density (Melquist, Hornocker, 1981). If the otters in the nest do make it to adulthood by avoiding the raccoons, they still have more to worry about. Raccoons are capable of physically harming an adult otter (Davis, 2008). Otters put themselves in danger when trying to defend their home and their nest. One study by H.B. Davis showed that elements such as greed, instinct and memory play roles in how a raccoon chooses its living environment. It is by pure instinct that any animal knows what type of place is the “right choice” when it comes to building a safe home. However, greed plays a role when it comes to sharing food or water, or even its territory with any other animals. Raccoons will take and take and take until they are completely satisfied (Davis, 2008). And their aggressive nature tends to make them lash out when confronted with a threat such as another predator (Davis, 2008). Raccoons are not going to want to share their food with river otters. Finding food becomes the main concern of the otter.
Although formal studies have not been completed, it has been noted that the crustacean population in the states of Colorado and Kansas has dropped dramatically in recent years (Boyle, 2006). In the state of Kansas, the raccoon population has exploded in urban areas (Rees et. al. 2008). In these same areas measures are being taken to reduce this population, efforts such as relocating the animals to places where they will have less human contact (Rees et. al., 2008). This relocation of raccoons and the recent crustacean population drop still have no proven correlation, but it is true that this lack of food will effect the otters whether the raccoons caused it or not. This drop in food supply forces the otter to search for other food items not necessarily in season at the time. This extra searching costs the otter precious energy. Energy that could be used to keep warm in the winter, build new dens in the spring, avoid predation or even to reproduce. Not only does the presence of the raccoon cause the otter to spend more energy finding food, but the raccoon is also a detriment to the otters health.
Toxoplasmosis gondii, or T. gondii is a strand of infectious disease that is caused by a parasite and is transmitted by fecal matter or direct contact. This disease causes changes in behavior of animals, loss of memory, inability to learn, and death to any fetuses present in the animal upon the contraction of this disease (Torrey, Yolken, 2003). If transmitted to a human this disease can cause death of fetus’, deafness, seizures, damage to the retinas, delusions and hallucinations along with a multitude of other serious symptoms (Torrey, Yolken, 2003). A study done in Illinois by MA Mitchell and his colleagues made a staggering discovery. Mitchell spent over five years trapping and testing raccoons in a state park. Out of a total of 497 raccoons caught, 17% tested positive for pseudorabies virus, 23% tested positive for canine distemper, and 52% tested positive for T. gondii (Mitchell et. al., 1999). With the existence of raccoons in the littoral zone now also comes the possibility for the spread of disease. A study done by ME Tocidlowski and his colleagues proved what many people had feared, the transfer of T. gondii to the river otter population. In North Carolina Tocidlowki trapped and tested 103 river otters and made the discovery that 46% of the rivers otters tested positive for T. gondii infection. This indicates that the otters had indeed come into contact with the infection and were now carriers (Tocidlowski et. al., 1997). With the risk of losing a fetus increased when carrying this disease, the otter population faces another problem when it comes to procreating. However, a study done by the same group of people has demonstrated the otters great ability to adapt. Of the 103 otters caught and tested by Tocidlowski and his colleagues 17% showed the presence of the T. gondii antibodies. Most of these 17% were juveniles who had probably been exposed to the disease as young pups but hadn’t actually contracted it (Tocidlowki et. al., 1997). It seems river otters have found a way to save their own population from a fatal disease, they have adapted to a new threat.
Yet, the North American river otter has not adapted only to this threat of disease. When it comes to the threats caused by the presence of raccoons in the littoral zone, river otters have almost mastered coexisting. Although raccoons do have an excellent sense of smell, otters have developed a way to safely protect their nests from the raccoons invasion, without putting themselves in the way of physical harm. Otters have been seen packing their nests with hundreds of leaves and sticks (Hansen, 2008). These leaves not only keep the nest warm in the winter, but they also keep the scent of the pups from leaving the nest. This insulation is something otters have developed to keep predators off of their scent trail. Adaptations like this allow the otters to protect themselves and their young and insure survival into adulthood. Once an otter has reached adulthood the main task becomes finding food.
When it comes to finding food, fish such as eels and minos, have become the main element in the river otters diet, but small crustaceans and other elements are still very important. A study done in 1996 by PR Beja showed how the otters were able to adapt their choice of food according to what is available at the particular season. During this study Beja introduced crayfish and other crustaceans into a river where fish was the main source of food for otters. Beja observed the otters feeding mainly on the crustaceans and crayfish upon their introduction. Once removed the otters then switched back to fish (Beja, 1996). This study highlights the otters ability to switch preferences and make changes in a diet where the preferred food source is not always abundant. This adaptation has also helped the river otter cope with fish and crayfish population changes during the winter and spring months. During these months crayfish and crustacean populations drop dramatically due to the cold and unstable temperature of the water in the rivers (Beja, 1996). However important fish are in the otters diets, there are other small plants and animals that are essential as well. Since the raccoon is busy hunting this prey from the land the otter has developed some other ways to hunt. The thick fur on the underside of an otters belly is an adaptation that was thought to keep the otter warm during the winter months when the water became extremely cold, but this fur provides more than just insulation for the otter. It actually works as a trapping mechanism for food. As the otter swims this layered fur snags little animals and plants holding them until the otter is ready to eat (Latch, 2008). Many otters are seen floating on their backs are picking out the food their belly fur has caught for them. This insulating belly fur demonstrates the versatility of one single adaptation.
Adaptations are not always changes in behavior. Physical adaptations such as good eyesight, hearing and smell allow the river otter to make full use of his senses, especially when trying to acclimate to changing environments. River otters have excellent eyesight in and out of the water (Hansen, 2008). This good eye sight allows them to close their ears and nose while hunting underwater. Keeping their sinuses and ear canals free of dirty water. Another physical adaptation of the otter is the placement of their ears, nose and eyes on their head. The otters nose is on the very top of the otters snout (Hansen 2008). This allows the otter to come to the surface of the water to breath without fully exposing itself to predators that may be lurking. The otters ears are also placed near the top of their head allowing the otter to come to the surface and listen and smell
for danger before exiting the water. These adaptations give the otter the perfect tools for avoiding predators and even confrontations with animals such as the common raccoon.
In the end, competition is natural. The species who is able to adapt to changes in the environment, food, habitat and competition will end up being the one that survives. Each of these species is simply doing what is natural. The raccoon is not living in the littoral zone to cause disease problems or lower population densities of otters, he is only trying to survive. The otters ability to adapt to these changes by finding new ways to hunt, build nests and protect their young is its way of adjusting to the change the raccoon has caused. The raccoon is simply adapting to changes occurring in his old urban habitat and the otter is adapting to changes in his new, raccoon filled, habitat. Changes are always occurring in nature, adaptations will always be a necessary part of change, and a necessary part of survival. If species like the North American River otter can not adapt to change then, like so many species before it, they too will go extinct.
Crait, Ben Jr. M. (2006). River otters in Yellowstone Lake depend on a declining cutthroat trout population. Journal of Mammalogy, 87(3), 485-494.
Davis, H.B. (2008). The Raccoon: A study in Animal Intelligence. The American Journal Of Psychology, 18(4), 447-489.
Gessner, M. O. (1999). Breakdown and nutrient dynamics of submerged Phragmites shoots in the littoral zone of a temperate hardwater lake. Science Direct, 112-224.
Hansen, Heidi. (2003). Food Habits of the North American River Otter (Lontra canadensis). Zoology and Physiology.
Lafferty, K. D., & Gerbert, L. R. (2002). Good Medicine for Conservation Biology: the Intersection of Epidemiology and Conservation Theory. Conservation Biology, 16(3), 593-604.
Latch, Ek. (2008). Deciphering ecological barriers to North American river otter (Lontra canadensis) gene flow. Journal of Heredity, 99(3), 265-274.
Maxfield, B., Bonzo, T., McLaughlin, C., & Bunnell, K. (2005). Northern River Otter Management. Utah Division of Wildlife Resources, 1-21.
Mitchell, M., Hungeford, L., Esker, T., Sullivan, J., Koerkenmeier, R., & Dubey, J. (1999). Serologic survey for selected infectious disease agents in raccoons from Illinois. Journal of Wildlife Diseases, 35(2), 347-355.
Reid, D., Code, T., Reid, A., & Herroro, S. (1994). Spacing, movements, and habitat selection of the river otter in boreal Alberta. CSA Illumina, 72(7), 1314-1324.
Torrey, E. F., & Yolken, R. H. (2003). Toxoplasma gondii and Schizophreni. Emerging Infectious Diseases, 9(11).
Zeveloff, S. I. (1988), Raccoons,1000-1023.