Birth Timing for Mountain Lions (Puma concolor ); Testing the Prey Availability Hypothesis Brian D. Jansen*, Jonathan A. Jenks Department of Natural Resource Management, South Dakota State University, Brookings, South Dakota, United States of America Abstract We investigated potential advantages in birth timing for mountain lion (Puma concolor) cubs. We examined cub body mass, survival, and age of natal dispersal in relation to specific timing of birth. We also investigated the role of maternal age relative to timing of births. We captured mountain lion cubs while in the natal den to determine birth date, which allowed for precise estimates of the population birth pulse and age of natal dispersal. A birth pulse occurred during June–August. Body mass of cubs was related to litter size and timing of birth; heaviest cubs occurred in litters of 2, and those born after 1 July. Cubs born within pulse months exhibited similar survival to those born out of the pulse. We found that cubs born April–June dispersed at younger ages than those born after 1 July. There was less variation in birth timing for 1st litters of females than older females. We hypothesize that cubs born after the peak in births of neonate prey are advantaged by the abundance of vulnerable prey and those cubs and mothers realize an evolutionary advantage. Citation: Jansen BD, Jenks JA (2012) Birth Timing for Mountain Lions (Puma concolor); Testing the Prey Availability Hypothesis. PLoS ONE 7(9): e44625. doi:10.1371/journal.pone.0044625 Editor: Marco Festa-Bianchet, Universite´ de Sherbrooke, Canada Received April 21, 2012; Accepted August 6, 2012; Published September 24, 2012 Copyright: 2012 Jansen, Jenks. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was funded by Federal Aid in Fish and Wildlife Restoration administered through South Dakota Game, Fish and Parks (Study Number 7587). The funders had no role in study design, data analysis, decision to publish, or preparation of the manuscript. The authors acknowledge that members of the funding agency participated in capture of study animals. Competing Interests: The authors have declared that no competing interests exist. * E-mail: bighorns101@yahoo.com Introduction Pattern of births for mountain lions (Puma concolor) is better characterized as a pulse over several months [1] than a sudden peak, characteristic of many ungulate populations [2]. Studies of mountain lions over numerous years have documented litters born in every month of the year [3]; however, the majority of births occur from June through October in North America [4]. Logan and Sweanor [1] hypothesized that because the pattern coincided with availability of young ungulates, that cubs born within the pulse had a greater chance of survival. However, Laundre´ and Herna´ndez [4] tested this prediction and concluded that there were no differences in survival related to timing of birth. Mountain lion cubs weigh about 400–500 g at birth [3]. Males typically outweigh females throughout their lives [1]. Litter sizes range from 2 to 4 cubs [1]. Despite existing information on reproductive ecology of mountain lions, the extent to which number of cubs in a litter influences birth weights is unknown. No study has sought to elucidate the age of dispersal in relation to the timing of birth, although geographic patterns of juvenile dispersal in mountain lions are adequately documented [5–8]. Juvenile mountain lions disperse about 1 month after becoming independent of mothers [7,8], and both sexes become independent at similar ages [1]. Males disperse farther than females [1,8,9]. The birth pulse in mountain lions has been previously investigated by summing all litters born regardless of maternal age or experience [1,4]. Parturitions have been documented an average of 3 months (mean birth interval - mean age of independence [17 - 13.7 = 3.3 months]) following departure of successful litters [1]. Mean gestation length for mountain lions is 3 months [1], thus subsequent litters begin close to departure of previous successful litters. Females that lost litters before cubs reached independence produced litters from 4–10 months later [1], suggesting a breeding lapse of 1–7 months following unsuccessful litters. Introduction of these variables into the birthing schedule suggests that birth timing through the year will become less predicable as females age. Our objective was to determine if differences occur in body mass at 1 week of age, survival to 1 year, and age of natal dispersal for mountain lions with respect to timing of birth. If timing of births is related to prey availability [1], then we expect a birth pulse (highest frequency of litters born) coincident with availability of neonate ungulates. We expect heavier cubs and higher survival for those cubs born within the pulse. However, natal dispersal is thought to be related to timing of the mother’s estrous cycle [1]; thus, we predict no relation of timing of birth to age of dispersal. We predict that birth timing in younger females or first litters will be more precise than birth timing in older females of subsequent litters, because timing of subsequent litters depends on completion (i.e., mortality, independence) of the previous litter. Results Birth pulse We captured 42 litters from 2005 to 2009. We documented litters born in every month; however, frequency of litters produced was not uniformly distributed through the year (Fig. 1, 2 X 11 = 25.43, P,0.01). Months with higher than expected births included the period June–August; thus, we defined our birth pulse as occurring from 1 June to 31 August. We further delineated the year as spring (April–May), early pulse (June), middle pulse (July), PLOS ONE | www.plosone.org 1 September 2012 | Volume 7 | Issue 9 | e44625