This is the time of the year to be out in the woods.  No excuses.  The awakening of April has transformed itself into the emergence of May.  It is during this month that the 2006 generation will be out and about, taking advantage of the bountiful summer season of energy and growth.  The next four months will be a struggle for survival, growth, and preparation for the winter season of scarcity.

The new generation of mammals is out in display for the fortunate hiker.  Bear cubs have emerged with the sow in late April.  With the excellent forage offered in Pennsylvania, studies show that the rearing of five cubs is as likely as single cubs (about 6%).  Emerging mothers will either have the newborn cubs or the yearlings, who have spent the previous year with their mothers.  It is easy to distinguish between the 5 pound cubs and the 50 pound yearlings.  By the end of this month, the sow will chase off the yearlings, enabling her to find a mate to initiate her alternate year mating.  The dispersal of the young will follow an instinctual pattern, common among most mammals, with females settling along the periphery of the mothers range, and males forced to seek out more distant territories, beyond the range of existing males.  It is the result of these long treks that stories reach the press about these young males being found far from their usual habitats.

Coyotes have a late winter mating, resulting in one litter with an average of six young per litter per year (the largest litter recorded is 19), born in late April to early May.  This newly returned species is now found in every county of PA, MD, WV, VA and NC.  They’ve even been seen in Rock Creek Park and along the George Washington Parkway.

Red foxes have one litter per year, averaging five per litter (the largest litter being 17 pups). In our mid-Atlantic region, breeding begins as early as late December, peaking in January and early February with most birthing taking place in March.  Emergence from the den will take place in April. 

Gray foxes are about a month behind red foxes, producing one litter a year with an average of four (1-7) born from early April to May, with emergence in May.

Raccoons generally have one litter of 3 to 4 individuals, with mating taking place from late December to early March, peaking in February with most litters born from April to May.

Striped skunks have only one litter per year, with an average of four to six per litter.  The record brood was eighteen, set in PA.  The kits are born in May or early June.

Bobcats produce one litter per year, with an average of two or three cubs commonly born in April or May.

White-tailed deer have one litter per year with two per litter for mature adults, although 10-15% bear triplets, and rarely four are recorded. Single fawns will be produced by first litters, old does, and in poor seasons.  Most young are born in late May and early June in this Appalachian region. 

Mating shortly after spring emergence (late February  to early April), woodchucks have one litter of four to five, produced in April to mid-May. 

Even beaver usually have only one litter each year with three to four per litter. Mating occurs from December through February, with birthing from April through June.

But, not all mammals have just one litter per season.  And, within the same species, those living in southern climates may have more litters than their northern counterparts.  Below are some of the multiple brooders.  Many of these will have their first litters out prior to May.

For example, gray squirrels will normally produce two litters of about three (ranging from 1-9) per litter per year, with parturition (birth) about March and August.

Opossum will normally produce two litters with up to 13 per litter per year (a third brood can occur if an earlier brood is lost in the pouch stage).  They will breed from January through November with two periods of mating, usually in January/February and May/June.   Usually about 21 young are born after only a 13-day gestation (although up to 56 have been recorded), but the number of nipples limits the brood, with normally only an average of eight to nine in the Appalachian region (six or seven to the south) leaving the pouch (after 50 to 65 days on the teat).  Additionally, not all mammae are functional.  Newborn (rather, living embryos), all generally born within 12 minutes, are smaller than a honeybee.  Young are weaned after 90 – 100 days and are independent at 2 to 3 ˝ months.  For the first month out of the pouch, the young will hang onto the mother as she forages.  It is said that road killed females can occasionally have young still attached or still in the pouch.  Something to think about…

Most species of shrews have two or three litters of five to six (2-8) per litter per year, born from April through July.  The young of the masked shrew exhibit a "caravaning" habit of following-the-leader in a single file line, each one with its nose in the fur of the one in front of it.

Then there’s the rabbit.  Our eastern cottontail breeds throughout the growing season (from February through September) with three to five litters per year with an average of  5 per litter (can be as many as 12). 

But, if one were to guess that the highest fecundity of our native mammals belonged to the cottontail, they would need to learn more about the rodents.  In fact, the most prolific mammal in North America is the meadow vole.  Breeding for the vole occurs throughout the year (primarily April to November) with an average of eight or nine litters with a litter size of five to eight (1-11).  Such rapid births are the result of postpartum estrus, which enables a new pregnancy within hours of birthing. For the record, in a captive setting, one female had 17 litters in one year. 

As the above indicates, various strategies exist for securing the success of the progeny.  In general, the larger mammals have fewer young, while the smaller tend to have more and larger broods.  Both rabbits and hares produce relatively large litters and are prodigious reproducers, with large populations maintained; supplying a significant food source for many predators (high fecundity is balanced by high mortality).  This is known as an r-selected strategy.  The other primary reproductive strategy practiced by larger mammals are k-selected species, which produce low numbers of young, with a much greater proportion of the young entering the breeding populations.

Adding the multitude of fledgling birds and the amphibians and reptiles (not to mention the millions of new insects), it is somewhat astounding to realize that this same number of individuals must die each year in order to maintain a stable ecosystem.  Within this stable ecosystem, all the energy of the deceased is consumed by the living for their growth and reproduction.

So, make sure to get out in the woods to view the birthing of another season and another generation of nature’s life forms.  No excuses.  Celebrate birth.  Celebrate life.  And accept death, for death is, in the natural world, a part of life.