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About Medford mail tribune. (Medford, Or.) 1909-1989 | View Entire Issue (Feb. 11, 1958)
SIX MEDFORD (OREGON) MAIL TRIBUNE Tuesday, February II. 1958 Is That So? By EUGENE BURNS Ranger-Naturjiist One of the major ad vantages warm-blooded mam mals have is that the mother can carry her developing im mature young out of harm's way within her body and then give birth at that time of the year when survival is best assured. Unlike the human method in which the embryo develops steadily, day by day until birth, many mammals have developed astonishing varia tions which can delay birth from a few days to several months. This seems particu larly true in regions where winters have become more severe than they were in ages past, or where food is not plentiful during recurring seasonal periods, or where the mother is nursing or in poor condition. Although it is a matter of recent "discovery" there are three astonishing variations and they occur quite regularly In the wild animals about us. In one group, the egg is fertilized but then its normal development is arrested with in a few days. This includes the fisher, mink, badger, arm adillo, weasel, black bear and marten. In a second group, which includes deer, rat, mice and allied families, there may be a definite interruption of growth after-the embryo is already quite well developed the interval lasting from a few days to several months. With the third group, con fined to most bats, the egg it self is not fertilized until sev eral months after mating but once fertilized, develop ment is normal. Egg Fertilized To take the latter group first: most American bats, like our common brown bat, mate in the late summer or fall. As far as the egg is con cerned, nothing h a p p e n i. Then, months after mating, when springlike, balmy weather arrives, the egg is fertilized and a new life begins. Should the winter be prolonged, then fertilization will be deferred. Should spring be hastened, say by placing the female brown bat in a warm room, during any time of the winter, then ferti lization takes place and the young will be born approxi mately 90 days thereafter. In the second group, the egg is fertilized immediately but the period of gestation, as with the deer, may vary from 150 to 280 days! What hap pens is this: after the egg is fertilized and there has been a certain amount of develop ment, the embryo may be come dormant for four to five months particularly if the mother is in poor condition. Likewise should the weather turn cold suddenly, the bad ger may halt the growth of its embryo for at least 60 to this, the first group has a development within the egg a few days, then the quiescent period may last for weeks, sometimes even months. To all outward appearances, there is no change in the mother and the pattern of her behavior is un affected. But once growth of the egg is resumed, it always proceeds regularly thereafter, regardless. Among these ani mals is the marten, whose gestation is about 250 to 270 days roughly, 8Vz months, which seems excessively long for such a small animal. But yet, there is a much more commonly-observed ar rested development. It is the bird's egg which is fertilized when laid, yet no develop ment takes place until cer tain temperature requirements have been met for a certain number of hours. Were this not true, the bird s young would be hatching in the same nest continuously over a pro tracted period, and as a re sult, the first-born might die of hunger should the mother elect to hatch out the re mainder, or the unhatched young might perish within the egg should she elect to heed the importunings of the first-born. Copyright 1958, 0 by Eugene Burns) (Released by McClure Newspaper Syndicate) Free: By special arrange ment with the editors of the Encyclopedia Americana, my panel of judges will award each week to the reader who sends me the best true-life nature adventure, the best nature observation, or the best question on nature and wildlife, a complete 30-volume set of this world-famous reference work in a hand some Sealcraft binding. Each week ' new submissions will be considered. Sorry, I simply can't answer your many friendly letters. Please ad dress your letter to: Is That So! care Medford Mail Trib une, Box 575, Sausalito, Calif. Americans working on their television aerials at home suf fer more than 16,000 disabling mishaps a year. I now fate 3H6 ' Chevron flmm' 1 'A supreme 0m jjj Standard announces a new grade of gasoline . . . specially compounded to deliver more performance ;rom today s super cars . . . more value from your gasoline-dollar! Feeling adventurous? 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