CHAPTER 5 



REPRODUCTION AND FAWN MORTALITY 



Conception and Birth Dates 



Conception dates were calculated from fetal measurements 

 (Hudson and Browman 1959) for 32 litters; 9 from 1962-63, 14 

 from 1984-85, and 9 from 1985-86. Those data indicated 

 conception occurred from 15 November to 24 December with a 

 median date of 25 November. Seventy-five percent of litters 

 were conceived between 21 November and 1 December. Based on 

 a mean gestation period of 203 days (Robinette et al . 1973), 

 births would have occurred from 6 June to 15 July, with a 

 median of 16 June. These dates appear somewhat late for 

 conception and parturition, based on other data and 

 observations. Most fetuses were collected during 1984 and 

 1985, when deer were generally in poor condition and 

 conception and parturition may have occurred later than 

 average. Newborn fawns were observed as early as 2 June, 4 

 days prior to the earliest date projected by fetal 

 measurements . 



Birth dates calculated from the weights of fawns captured 

 during June (Robinette et al . 1973) were earlier than those 

 projected from fetal measurements. Few of the fawns were 

 newborn, and most were at least several days old; weights 

 ranged from 2.7 kg to 9.3 kg (X = 5.4, SD=1.4, n=194). Birth 

 dates calculated by this method project only the early end of 

 the range because fawns were born after capture operations 

 ceased. The earliest was 27 May and 33 (23%) of 146 litters 

 were born prior to 6 June. Considering all data, we estimate 

 parturition to occur between 27 May and July 15, with a median 

 of 10-12 June. The corresponding median date of conception 

 was 20-22 November. 



Although the general time of breeding and conception is 

 probably established by photoperiodism (Verme and Ullrey 

 1984), dates of conception within any local area may be 

 influenced by nutrition and age, among other factors (Verme 

 1965 and Robinette et al. 1973). Both Verme (1965) and 

 Robinette et al . (1973) indicated that well nourished females 

 gave birth earlier and/or had a shorter gestation period than 

 females on a lower nutritional plane. The effect of the dam's 

 nutritional status on birth weights of fawns is not clear 

 (Verme 1965 and 1969, Murphy and Coates 1966, and Robinette et 

 al. 1973). Available evidence suggests that a threshold birth 

 weight may exist, and within limits, the gestation period is 

 longer and fetuses are smaller among females on a lower 

 nutritional plane. 



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