Understanding the mechanisms which control reproduction in lynx is essential for their continued viability and effective conservation. Recently, a team of European researchers may have found a key to improve the lynx’ reproduction rate.
They discovered that the of the Eurasian lynx (Lynx lynx) has the longest lifespan among mammals known to date. This hormone producing tissue is responsible for restricting the Eurasian lynx (and presumably the Iberian lynx as well) to only having one oestrous cycle per year (mono-oestrous) and therefore only one opportunity per year to become pregnant. The findings were published on 5 March in the scientific journal PLOS ONE.
The scientists from the Leibniz Institute for Zoo and Wildlife Research in Berlin (IZW) took the Eurasian lynx as a “model” species. They investigated the reproductive cycle of these lynxes in order to assist in the conservation of the highly endangered Iberian lynx (Lynx pardinus), the most threatened cat species worldwide. Currently 149 specimens live in captivity on the Iberian peninsula, while only 309 still live in the wild mainly restricted to two isolated population in southern Spain. These numbers are not sufficient for the survival of the species in the long term and experts agree the cat is now on the brink of extinction. A key component in the conservation strategy for the Iberian lynx are the captive breeding centres in Spain and Portugal where Iberian lynx are bred in order to be re-introduced back into the wild. Improving reproductive performance in captivity entails a thorough understanding of the mechanisms that facilitate reproduction in these felids.
Video of mother ‘Boj’ playfighting with one of her cubs born in 2012 at one of the breeding centres on the Iberian peninsula:
(Source: Programa e Conservación ex-situ, Lince Ibérico)
The team’s key discovery is that lynxes have a reproductive strategy unique for felids — and probably for mammals in general. The lynx has corpora lutea (CLs) which are maintained in their ovaries over many years — the longest lifespan known in mammals, while in other species, the CLs disappear before, or shortly after, the female gives birth. Surprisingly, the female lynx can switch off its CL’s progesterone production when entering a new cycle during spring or before giving birth without destroying the CL. Later on, progesterone is produced continuously, suppressing the follicular development in the ovary and therefore preventing the onset of a second oestrus cycle within the same year. If a female cannot mate during its 5 — 7 fertile days per year (oestrous period), an entire reproductive period will therefore be lost, reducing fertility and effective lifetime reproductive output, a substantial problem for a small population such as the Iberian lynx.
“To obtain these results, our international team followed the reproductive cycles of captive Eurasian lynx in German zoological gardens and of free-ranging Eurasian lynx in Norway with the help of a Norwegian wildlife research project, Scandlynx, over a period of almost three years,” says veterinarian scientist Johanna Painer from the IZW. They used advanced three-dimensional ultrasound techniques and in-house hormone analyses to uncover the mysterious development of the oestrus cycle.
Europe is home to two Lynx species, the Eurasian lynx and the Iberian lynx. Both species experienced drastic declines in population size during the last century. Whereas the Eurasian lynx recovered in many parts of its European range with the help of re-introduction projects, the population of the Iberian lynx crashed completely. It is listed as Critically Endangered by the IUCN Red List of Threatened Species™.
It is unknown to what extent lynxes will have the flexibility to adapt their reproduction to anthropogenic environmental changes. This study provides essential information for the assisted reproduction techniques in Iberian lynx which continue to be refined and improved, such as artificial insemination or embryo-transfer. Future research will focus on the manipulation of reproductive cycles to increase the reproductive output for breeding centres and to discover the molecular mechanism underlying this unique phenomenon.
(Source: Forschungsverbund Berlin e.V. press release, 05.03.2014)