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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 Cor­pus Luteum 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)