Thursday, May 1, 2014

Birth, Death & Survival

Following the gradual thaw of March and the steady transition of April, an explosion of life occurs in May and June across the Northern Hemisphere.  More direct solar radiation supplies the energy, warming the landscape, igniting thunderstorms and fueling photosynthesis; the latter, which takes place in the leaves and stems of green plants and in the cells of cyanobacteria and algae, utilizes water and carbon dioxide to produce glucose and to enrich the atmosphere with oxygen.

In turn, insects, certain reptiles and many birds and mammals feast on those plants, including their nectar and fruits.  The insects, having overwintered as eggs or having emerged as nymphs from ponds, soil or rotting vegetation, begin to reproduce and provide food for carnivorous plants, larger insects, fish, amphibians, reptiles and insectivorous birds and mammals; fish and amphibians also provide sustenance for a host of reptiles, birds and mammals.  Finally, reptiles, birds and mammals feast on one another (herons on lizards, otters on turtles, gators on muskrats, snakes on nestlings, hawks on mice, etc.).

For any given species, survival is dependent on a reproductive rate that outpaces (or at least matches) the loss of individuals to predation, injury, illness and advanced age.  At the bottom of the food chain, plants and a host of invertebrates (including worms and insects) are highly prolific, as are primary consumers such as mice, cottontails, frogs and fish.  The higher a species lies on the food chain, the lower its reproductive rate tends to be; indeed, apex predators are especially dependent on the reproductive success of their prey species since their own reproductive rate is often governed by prey availability.