include foxes, snakes, weasels, hawks, owls, domestic dogs, and domestic cats. To avoid predation, wood mice tend to forage in covered microsites. Reproduction The wood mouse has a breeding season from February to October in which multiple matings occur between males and females, resulting in scramble competition. Such behavioral characteristics result in sperm competition and multiple paternity litters. The society is polygynous with copulation resulting from scramble competition during reproductive periods. Males possess a sac known as the cauda epididymis, which stores sperm and lies underneath the scrotal protrusion. Temperature regulation ensures maximum sperm output. One interesting observation about the species, in particular the males, is the morphology of the spermatozoa. They develop falciform (sickle-shaped) heads after meiosis and before spermiation (release during ejaculation). The hook located at the tip of the head adheres to the surface of the head prior to deployment. Propidium iodide staining revealed that only the basal surface of the hook is of nuclear origin. These apical hooks are deployed in the female reproductive tract (the mechanism responsible involved the remodeling of actin filaments in the hook). Deployed apical hooks combine with apical hooks and flagella of other spermatozoa. The aggregates of spermatozoa that result in form "mobile trains", which have experimentally been determined to possess better motility in the female reproductive tract. The mobility of these mobile trains was also found to be influenced by premature acrosome reactions, altruistic acts performed by some spermatozoa for the benefit of other genetically similar gametocytes. This altruism follows a "green beard" mechanism in which spermatozoa discern the genetic similarity of surrounding gametocytes (such mechanisms are rare because they must code for a recognizable phenotype, as well as response mechanisms). Once spermatozoa of similar genotypes are identified, altruism genes are turned on to elicit a response that seeks to conserve the genes present in the other cell, even if it results in the destruction of the cell performing the action. The gestation period of wood mice is of 25–26 days and each female produces on average four young per year. The offspring become independent after about three weeks and become sexually active after two months. Gallery Further reading Fairley, J.S. 1975. An Irish Beast Book. Blackstaff Press Limited. SBN 85640-090-4 References External links Apodemus sylvaticus in the Smithsonian Museum of Natural History MSW Scientific Names Apodemus sylvaticus in the Catalogue of Life: 2007 Annual Checklist Apodemus sylvaticus in Fauna