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Interactions between species such as the bee and the flower, and the squirrels of the Mojave desert, show a form of compatibility that has allowed their coexistence. Interactions between bees and the flowers are positively beneficial, so that both species not only coexist in nature, but are also totally dependent upon the other's existence (interdependent). The same occurred very long ago with the chloroplasts of plants and the mitochondria of mammalian blood, that have their own DNA rings, showing that they were separate species in our distant past. (Chloroplasts are the cellular structures (organelles) that capture light energy during photosynthesis and mitochondria are the cell organelles of vertebrates that serve to convert energy bound in foods to useful forms of energy for distribution throughout the body). Two squirrels of the Mojave desert, the antelope squirrel (Citellus leucurus) and the Mojave squirrel (Citellus mojavensis), would live quite well without the other's presence, but through intense interactions with each other and a demanding environment, have evolved a compatible behavioural mechanism, that I will soon describe.
A study of nature shows many examples of behaviour that speads a population out in some way so that the number of individuals is under the carrying capacity of the environment. Distribution statistics often show that a species is at a lower density than would occur under conditions of random association. The most common behaviour employed to spread a population out is territoriality.
Where environmental conditions such as temperature or available water are extreme, population numbers are usually controlled by such environmental vagaries. Harsh environments tend to cause very high mortalities in both the new offspring and throughout the population. However between the periods of harsh conditions are periods of calm where the species can flourish. As habitats subject to harsh conditions are also quite fragile and easily disrupted through over-exploitation, some species may also require behavioural mechanisms that will hold population numbers below the carrying capacity during the more mild periods.

Mountain goat:
One such species is a beautiful mountain goat, Oreamnos americanus, found naturally from the northwestern United States, through Canada to Alaska and introduced to other mountainous western states. This animal copes with extreme cold, sparce food supplies, avalanches and the danger of falling off the sheer mountain faces. A short study of this species showed that of the adults found dead, 60% had been killed by avalanches and 15% by falls (Chadwick, 1978). Over half of the kids and yearlings die during the harsh winters. These non-living factors that affect an animal are called abiotic factors. In this extremely harsh climate, temperatures can fall below minus 45^oC, but the animal is adapted to this, through a specialised double coat. It has a top coat of long hollow hairs that overlay a thick, fluffy underlayer. The goat feeds on over 170 plant species and has specialised rock climbing hooves, with two toes with traction pads that can be widely splayed or used to grip.
With such a high mortality rate due to abiotic factors, one would expect all the goat's efforts to focus on maximising reproductive output during the warmer, more benign periods. However goat behaviour could only be related to factors within their whole environment. The animals were highly combative, but with the largest, most powerful billies behaving as subordinates to the smaller nannies. Kids and yearlings were very playful and active, approaching even the oldest nannies in play. Up to two and a half years of age juveniles would challenge any other goat. Adults were often preoccupied with ritualised back arching and attempts to gore the rivals flanks. Individual goats seemed to constantly test their position within the group's social hierachy. From about two and a half years of age, the onset of sexual maturity led to males being less confrontational and retreating from challenges from smaller goats and eventually becoming solitary, leaving the female-subadult bands. The social and environmental impact of this change in behaviour is that the mature males did not compete directly with mature females and young goats for forage.
Fighting occured frequently between bands, spreading them apart, over their natural range, in a dispersal that was wider than that through simple random association. Animal distribution was a function of intraspecific behaviour rather than available food. Their behaviour served to reduce competition for food and shelter and prevented the overexploitation of their food resource! Nannies held the highest position within the social hierachy, so ensuring access to whatever food was available. In this way the fittest breeding female's perpetuation is ensured, while some compatibility with the natural habitat is maintained. A breeding male could fertilise many females, so even if many died, the survivors would represent genes best adapted to the harsh climatic conditions. The amazing behavioural repertoire of this species reflects its adaptation to its harsh climate with few predators. When humans impinge on this beauty and start taking trophies, the population declines.

Desert Squirrels:
In the Mojave Desert of California, two species of ground squirrel, the antelope squirrel (Citellus leucurus) and the Mojave squirrel (Citellus mojavensis), coexist under harsh conditions. Scientists initially assumed that the smaller, more active antelope squirrel excluded the larger and less active relative from its territory through competition, and higher reproductive output, but they live together in their natural surroundings without interactive detriment or competition (de al. Feunte, 1971). The solution, resulting in this compatibility, can only be understood through the holistic perspective of looking at the whole environment of the animals.

Both animals are diurnal omnivores that do not need much water. They have adapted to cope with the high temperatures and dry conditions typical of the desert. Antelope squirrels and the Mojave squirrel possess different physiological and behavioural adaptations to heat and drought. If the physiological mechanisms of the antelope squirrel begin to fail under extreme conditions, it resorts to a behavioural solution to stay cool. If it cannot control its over heating by finding a refuge, it begins to produce saliva, wiping this over its head area until it is completely wet. This allows it a period of grace to find a better refuge, at the cost of some moisture.

Mojave squirrels copes with drought by spending seven months of the year (August to March) in a state of intermittent sleep called aestivation. It sleeps for between three and five days per week during this period. Between sleeping it goes about its normal activities. Each sleep phase lasts about six hours, its temperature drops to below the surroundings, oxygen consumption decreases, breathing and heart rate slow and very little energy is used. Over 172 days, it needs only 2 oz of energy in this state and normally carries at least 4 oz of fat.

Antelope squirrel numbers are limited by the months of food shortage during the same months when the Mojave squirrel goes into its state of aestivation. From April through to July, food is plentiful and the two species coexist, feeding on the same food resource. During the period of insufficient food the two species cannot coexist. Aestivation is partly a response to abiotic factors but biotic interactions must have also been a selective "force" leading to the solution displayed. The Mojave squirrel has managed to reduce the "cost" of interactions with the Antelope squirrel, by reducing competitive interactions for food and appearing during times of plenty. I call this a reduction of the i-factor (interactive factor). What a solution to competition - compete better by going to sleep and not interacting, for to interact with a more efficient animal is a waste of energy! This is why "competition" is such an unsuitable term for interactions in nature. Which of these two species is the better competitor?

The evolution of coadaptations is the result of the evolution of improved economic efficiency! Just as an animal that evolves a better camouflage has an improved survival potential, so the animal that evolves a more (energetically) efficient interactive mechanism is better adapted to its environment. Two different species, or individuals of the same species, may adapt to each other in this way, evolving an association that is efficient and reflects interdependence.
Even humans are locked into this evolving dependence and interdependence with other species. In many parts of the world, populations are dependent upon maize, while maize is so specialised that it depends fully on humans for its dispersal. Genetic modification and bioengineering, such as is happening on a large scale to most crops, is removing these crops further from their natural state and so making them more dependent on humans for their survival. It would be safer for humanity to adapt its behaviour to rely upon less specialised and modified crops and ecosystems for survival. With the creation of special varieties, bio and genetic diversity is lost, so reducing future adaptive options. Genetically modified crops are forever different and the long term consequences are unknown.


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