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| Goitom, A.H. | |
| Identification of the putative urinary intraspecific recognition pheromone of the caracal _Caracal caracal_ | |
| 2017 Full Book | |
Sheep husbandry makes a considerable contribution to the economy of South Africa. However, it has been pressure during the last few decades due to the rapidly growing numbers of predators such as the caracal, _Caracal caracal_, and the red jackal, _Canis mesomelas_. Currently, sheep farming is hardly viable in the arid southern parts of the country. When experimenting with various methods of controlling caracal numbers, sheep farmers found that this problem animal could be effectively lured into traps using the urine of another male or female caracal. The main disadvantage here is that a sheep farmer could incur serious stock losses before he is able to obtain a starting sample of urine from another source (e.g., another farmer). It was hypothesised that caracal urine contains a volatile organic substance, or substances (VOCs), that are involved in the semiochemical communication between members of this species. The objective of this investigation was to identify these putative attractants in the urine, for the subsequent formulation of a caracal lure composed of synthetic analogues of the natural VOCs. As sheep farmers reported that male and female urine were equally effective attractants, it was considered unlikely that the attracting agent could be a sex pheromone; rather, it could have an intraspecific signalling function. Efforts were made to identify all the VOCs present in caracal urine samples donated by farmers from different sheep farming areas of the country. A total of 191 VOCs, including five steroid hormones, were identified. The identification of 86% of these VOCs was corroborated by gas chromatographic-mass spectrometric (GC-MS) comparison of the natural substances with authentic synthetic analogues. Obligate proteinuria is known in certain animals, in which it is not an indicator of renal abnormality. In the house mouse, Mus domesticus, for example, so-called major urinary proteins (MUPs) bind dehydro-exo-brevicomin and 2-(sec-butyl)-4,5-dihydrothiazole elicit male aggression. The carboxylesterase-like urinary excreted pheromone-binding protein, also known as cauxin, has been identified in the urine of several felids, but was not found in caracal urine. However, the pheromone-binding proteins 'Transgelin fragment (M3WJ37)' and 'Uncharacterized protein (M3XEJ0)', both previously identified in Felis catus and _Felis silvestris catus_, were identified in caracal urine. The macrocyclic C15 ketone, cyclopentadecanone, was identified as one of the VOCs present in the headspace gas of caracal urine. The headspace concentration of this ketone increased when the urine was heated at 95 §C for 10 min. A similar, but more pronounced increase in cyclopentadecanone concentration was observed when urinary protein present in caracal urine was denatured by subjecting it to similar treatment. This was interpreted as an indication that this ketone is a ligand of caracal urinary protein. The C13, C14, C16, and C17 macrocyclic ketones were subsequently also identified as urinary protein ligands. In bioassays, a mixture of synthetic analogues of a large number of the other ketones identified in caracal urine, including cyclopentadecanone, elicited typical feline behaviour in two male caracal in captivity. Similar behavioural patterns were observed when a mixture of the C13, C14, C15, and C16 macrocyclic ketones were tested. It was concluded that these ketones, that are ligands of the caracal's urinary protein, could play an essential role in the intraspecific communication of the caracal. |
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