Why captive African male lions hit puberty earlier than wild lions, some at just 1.2 years of age? Here’s what researchers found

Male African lions in captivity reached puberty at a younger age than wild-born lions, a study found that examined hormone levels, body weight and the presence of sperm in male lions. The research, published in PLOS ONE in 2019, looked at reproductive development in male African lions and found that puberty occurred earlier among captive-born males. The researchers also found a link between the onset of puberty and body weight, or growth rate.

The findings provide physiological data on a stage of lion development that, according to the researchers, had previously been understood largely through behavior and physical changes.

Captive-Born Male Lions Reached Puberty Before Wild-Born Lions

The most striking finding was the difference in the reported age of puberty between captive-born and wild-born male lions.


According to the study, puberty occurred in captive-born males at less than 1.2 years of age, while it occurred in wild-born males at less than 2.5 years of age.

The researchers also found that sperm was observed in captive males as young as 1.2 years. In wild males, sperm was observed in ejaculates at about 2.5 years.

The study therefore identified an earlier onset of reproductive development among the captive-born males examined.

The Study Looked at More Than Just Hormones

To examine reproductive development, the researchers used several types of measurements.

They analyzed fecal androgen metabolites and fecal glucocorticoid metabolites from 21 male lions at 17 institutions. The lions ranged from 0.9 to 16 years old, and samples were collected over periods ranging from 3.8 months to 2.5 years.

The researchers also collected body-weight data from 10 individuals at five zoos. Those animals were between 0 and 3 years old.

Urine samples were collected from six males at two facilities to look for spermatozoa. The urine assessment included males between 1.2 and 6.3 years old.

Overall, 26 male African lions at 18 accredited institutions were included in the study, although different groups of animals were used for the hormone, body-weight and urinalysis portions of the research.

Captive Lions Gained Weight Faster in Their Early Years

Body weight was another important part of the research.

During the first two to 2.5 years of life, captive male lions gained an average of 7.3 kilograms per month. Wild males gained an average of 3.9 kilograms per month over the same period. So the researchers concluded that the onset of puberty was influenced by body weight and growth rate.

The study found an association between earlier puberty in captive-born males and faster growth observed in captive group. It did not simply establish that captivity itself caused puberty to occur earlier.

Lion's Hormone Levels Increased Around 2 Years of Age

The researchers also tracked fecal androgen metabolites to examine changes in reproductive hormones as the lions aged.

An increase in the overall mean fecal androgen metabolite concentration occurred at about 2 years of age. After that point, concentrations remained similar throughout adulthood.

The study found differences in fecal androgen metabolite concentrations between the peripubertal group and the older age groups. By contrast fecal glucocorticoid metabolite concentrations did not differ significantly among the age groups.

The researchers also reported no difference in fecal androgen or glucocorticoid metabolite concentrations based on season.

Sperm Provided Another Sign of Reproductive Development

The presence of sperm offered another way for the researchers to examine when male lions became reproductively mature.

Urine was used as a non-invasive method to assess spermatozoa. The study found sperm in captive males as young as 1.2 years old.

For wild males, the researchers referred to sperm being observed in ejaculates at approximately 2.5 years.

The findings supported the study's assessment that captive male lions attained puberty earlier than their wild counterparts.

What the Researchers Found About Puberty and Growth

The study's findings brought together several measurements rather than relying on a single indicator of puberty.

The researchers found that captive male lions attained puberty earlier than wild counterparts, while also observing faster weight gain among captive males during their first years.

They concluded that the onset of puberty was influenced by body weight specifically growth rate. They also found that spermiogenesis could be confirmed through urinalysis.

The researchers said that understanding the connection between body weight and the onset of puberty could help with reproductive management of lions kept outside the wild by helping mitigate the risk of unintended breeding among young animals.

How the Study Measured Lion Development

The research relied on non-invasive monitoring. Fecal samples were collected approximately twice a week from the lions used for hormone assessment, while body weights were obtained approximately monthly for the animals included in the weight analysis.

The study's researchers divided the male lions into reproductive life-stage groups for analysis: peripubertal animals from 0.91 to 1.99 years, subadults from 2 to 2.99 years, adults from 3 to 10.99 years and aged animals older than 11 years.

The study defined puberty as the process of acquiring reproductive competence. In male lions, this can involve the development of secondary sexual characteristics, mounting behavior, the appearance of sperm in urine or ejaculate, and the ability to ejaculate.

What the Findings Showed About Captive Male Lions

Taken together, the study reported a clear difference in the timing of reproductive development between the captive-born and wild-born male lions examined.

Captive-born males reached puberty at less than 1.2 years of age, compared with less than 2.5 years for wild-born counterparts. Captive males also gained weight more quickly during their early years, averaging 7.3 kilograms per month compared with 3.9 kilograms per month among wild males.

The researchers linked the onset of puberty to body weight and growth rate and used sperm detected through urinalysis as another measure of reproductive development.

The research was published July 3, 2019, under the title “Linkage between fecal androgen and glucocorticoid metabolites, spermaturia, body weight and onset of puberty in male African lions (Panthera leo).”