Reproductive physiology studies and associated technologies increase the success rate of any captive-breeding programme and are important in helping with the conservation of wild felids in captivity. Reproductive technologies are available for three major purposes: (1) assessing fertility and monitoring reproductive status; (2) assisting in breeding and maintenance of gene diversity; and (3) learning more about reproductive mechanisms of the endangered Iberian lynx.
Consistent with the need for more basic species information, our husbandry and breeding efforts have established/reconfirmed normative data on sexual maturity (males, 2-3 years; females, 2-3 years), oestrus length (3-7 days), copulations per pairing (avg. 28) and gestation interval (63-66 days). Faecal hormone monitoring has demonstrated that females experience ovarian cycles from January through May whereas males maintain testosterone year-round. But species peculiarities also have been revealed, for example, oestrogen metabolite concentrations during pregnancy are significantly greater than in other felid species. Additionally, progestin excretion profiles are unusually lengthy, largely because ovarian corpora lutea (sites of earlier ovulations) remain active much longer than in most other felids. Prolonged non-pregnant luteal activity has also been described in the closely related Eurasian lynx and in the Canada lynx suggesting an idiosyncratically-conserved mechanism for lynxes in general.
Regarding male reproductive physiology, sperm traits seen in the Iberian lynx are lower than those reported for some other felid species, yet higher than those reported for the Eurasian lynx and the bobcat. It has also been found that thawed-out Iberian lynx spermatozoa are capable of fertilising viable in vitro matured domestic cat oocytes, thus opening up the possibility of examining functional capacity of spermatozoa from this species under laboratory conditions.
The ex situ population is also being used to explore a novel means of diagnosing pregnancy. Because all ovulating lynxes produce rising progesterone (regardless of conception), conventional hormone monitoring is not useful for identifying a gestating female. However, increasing concentrations of the hormone relaxin (in blood or urine) are indicative of pregnancy in felids. A unique non-invasive means of collecting blood has been developed using blood-sucking Triatomine bugs (Rhodnius prolixus or Dipetalogaster maxima) placed in specially-drilled hiding holes in the lynx’s cork nestbox. As much as 2 ml of blood can be extracted per bug, more than adequate for the assay. Urine is captured using special collection devices distributed throughout the animal’s enclosure. Pregnant females express a positive relaxin signal from 32 to 57 days post-copulation of a 65-day gestation thereby allowing managers to prepare for an impending parturition.
In order to assist breeding and maintaining genetic diversity, the Iberian Lynx Ex situ Programme collaborates with the maintenance of Biological Resources Banks (BRBs) for conservation of biomaterial gathered from wild and captive Iberian Lynx populations. Biomaterials are presently being safeguarded at two locations: the National Museum of Natural Sciences in Madrid and the Miguel Hernández University in Elche, Alicante. Although the Museum of Natural Sciences places special emphasis on reproductive samples and the MH University focuses on multipotential somatic cells, both banks preserve tissue, blood, serum, and other biological materials. The conservation of gametes will allow the Breeding Programme to extend future options without the limitation of space or the risk of disease transmission, while opening the opportunity of prolonging the possibilities of reproduction for individual animals after their death. The storage of samples at both BRBs provides a safety net for these valuable materials and ensures that biosamples will be available for additional analysis whenever needed, which is a crucial resource for potential retrospective studies.