<p><em>By Kymberlee Nelson<br />
Keeper in Heart of Africa, Collections Husbandry and Science<br />
San Diego Zoo’s Wild Animal Park, Escondido, CA</em></p>

<h3>Abstract</h3>
<p>Following SSP&reg; recommendations two, 3&frac12; year old, female, Transvaal lions (sisters) were bred to a 3&frac12; year old male. These pairings resulted in two litters (2.2 and 1.2) born four days apart. Following the behaviors of lions in the wild, the two litters, dams and sire were successfully introduced to form one large pride.</p>

<h3>Introduction</h3>
<p>Lions are the only truly social cats living in groups called prides. A pride is generally composed of a group of related females and several non-related males (although males are generally related to one another). The African lion is listed as vulnerable in the IUCN Red List and can be found in Appendix II of CITES. The AZA felid TAG set a target population size of 350 lions; both generic and pedigreed animals. Currently, there are 133 lions at 43 institutions managed by the Species Survival Plan (SSP&reg;), with a target population of 150 cats (SSP&reg; 2007).</p>

<p>Captive breeding is determined by genetic analysis of the population with a goal of retaining 90% gene diversity for 100 years. The captive pedigreed population descends from 52 founders and is tracked and managed by the species coordinator and SSP&reg; Institutional Representatives. A Master Planning meeting is held each year where breeding recommendations and animal transfers are made.</p>

<p>In the wild it has been shown that females younger than 36 months rarely conceived (Hanby &amp; Bygott,1987) and that the mean age of first reproduction for females was between four (Bertram, 1975; Hanby &amp; Bygott, 1987) and six and a half years (Packer <i>et al.</i>, 2001). In captivity this age is reduced and reproduction is seen as early as 18 months. Wild females generally come back into estrous when their cubs are 18 months old (about 10 months from the end of lactation) and her next litter can be expected to be born 24 months after the birth of any surviving cubs (Bertram, 1975).</p>

<p>[caption id="attachment_372" align="aligncenter" width="300" caption="Arial View of Lion Camp"]<img src="http://dev.aecetia.net/gws/aazk/wp-content/uploads/arial-view-of-lion-exhibit-300x225.jpg" alt="Arial View of Lion Camp" title="Arial View of Lion Camp" width="300" height="225" class="size-medium wp-image-372" />[/caption]</p>

<p>Female pride members have been observed to come into estrus synchronously and therefore birth synchrony has been observed (Bertram, 1975; Packer &amp; Pusey, 1983). The female typically births one to four cubs in a secluded area away from the pride. It is not until the cubs are four to six weeks old that their dams will introduce them to the pride (Bertram, 1975; Packer &amp; Pusey, 1983; Pusey &amp; Packer, 1994). At this time, the dams and cubs will often form or join a cr&eacute;che, with cubs varying in age up to 150 days (Pusey &amp; Packer, 1994). Cubs will also be introduced to pride males, but the males play no role in the rearing of the offspring. The sire's primary responsibility is to provide a secure territory for the females of his pride and their offspring.</p>

<p>The main advantage to forming a cr&eacute;che appears to be the communal defense of the cubs against invading males (Pusey &amp; Packer, 1994). Females of the same cr&eacute;che are known to associate closely with each other. Generally all females are present with their cubs or all are absent, leaving the cubs unattended for short periods of time (Pusey &amp; Packer, 1994). Females in a cr&eacute;che will allow cubs of other females to nurse. There is evidence, however, that females can distinguish between their own offspring and other cubs, but are virtually indiscriminate with cubs of first order relatives (Pusey &amp; Packer, 1994). Cubs wean at six to eight months of age, but will begin eating meat at two to three months (Bertram, 1975; Pusey &amp; Packer, 1994); although cubs remain dependent on their mothers for two years (Bertram, 1975; Pusey &amp; Packer, 1994; Packer &amp; Pusey, 1997).</p>

<p>Average age of dispersal from the natal pride is two to four years for males (Pusey &amp; Packer, 1987) but males as young as 13-20 months may be forced out as a result of a pride takeover (Packer &amp; Pusey, 1983) and no males were observed with their natal prides past 65 months (Hanby &amp; Bygott, 1987). Most females are integrated into their natal prides but for those who emigrated all had left by four years of age (Hanby &amp; Bygott, 1987; Pusey &amp; Packer, 1987).</p>

<h3>Methods and Results</h3>
<p>Following SSP&reg; recommendations two, 3&frac12; year old, sibling female, Transvaal lions, Mina and Oshana, were bred to a 3&frac12; year old male, Izu. These pairings had previously resulted in Oshana giving birth to 0.2 on 16 May 2006 and Mina to 2.1 on 19 July 2006. The females were separated from their litters on 14 July 2007 due to...</p>

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