Substrate selection for urine spraying in captive wildcats

1. What they did

Urine spraying is thought to be the main way cats leave scent marks. A spraying wildcat raises their tail and squirts urine backwards onto a prominent object. The authors wanted to know what makes a plant a good place to spray, and predicted that wildcats would choose plants that make the mark easier to find, spread its scent further, or make it last longer: taller, wider or unusual plants, plants exposed to the wind, or plants with dense foliage or with a high content of volatile organic compounds (VOC) that slow down oxidation.

The study took place at a wildcat breeding centre in Lleida, Catalonia, Spain, which held 14 wildcats (four males and 10 females) in six outdoor enclosures. Four enclosures held one male and two females each, and two held a single female. The groups stayed the same throughout the study. As enrichment, 95 trees and bushes of 16 species had been planted across the enclosures.

Every morning from April to June 2005, after most kittens had been born (to avoid disturbing pregnant females), the enclosures were checked for plants that had been sprayed. A sprayed plant was recognised by a strong smell or by a typical pattern of dead leaves, and each plant was counted only the first time it was found marked. For every plant they recorded species, maximum height, maximum width, shape and foliage density, and for sprayed plants the height of the mark. They then tested which of these features predicted whether a plant was sprayed.

2. What they found

• 12 of the 95 plants were sprayed at least once, one to four per enclosure.
• Only three species were used: common juniper (7 of the 12 marked plants, 58.33%), box wood (4, 33.33%) and strawberry tree (1, 8.33%).
• Every common juniper in the enclosures (7 of 7) was sprayed, compared with 28.57% of box wood (4 of 14) and 10% of strawberry trees (1 of 10).
• The best statistical model kept only plant species. Knowing whether a plant belonged to one of these three species correctly classed 94.7% of all plants, and 58.3% of the marked ones.
• Selection index: common juniper was clearly selected (mean index 0.90 out of a maximum of 1). Strawberry tree was avoided (-0.78). Box wood was used about in line with how common it was (-0.21, not different from no selection). All other species were never used.
• Marked and unmarked plants did not differ in height or width, and shape and foliage density did not predict marking.
• The cats sprayed at an average height of 56.67 cm (range 25 to 75 cm).
• Repeated spraying of the same juniper left a patch of dead leaves at its base, which the authors put down to the fatty acid in the urine. A wildcat was photographed rubbing against such a plant.

3. What they concluded

• The captive wildcats chose where to spray by plant species, not by the plant’s size, shape or foliage. Choosing marking posts by plant species has rarely been documented in carnivores.
• Visibility and wind spread of the mark probably matter in the wild, but are likely irrelevant in small enclosures, and the three marked species were similar in how conspicuous they were.
• Common juniper is known from other studies to contain high levels of VOC with antioxidant activity, such as alpha-pinene; strawberry trees have such compounds in smaller amounts. The authors did not measure plant VOC themselves, but suggest that wildcats can recognise a plant’s VOC (as cats do with catnip) and choose plants that may slow the breakdown of the urine mark and so make it work longer.
• Wildcats in the wild, with many more plant species, sizes and arrangements to choose from, could behave differently. More studies are needed on plant VOC, how often each plant is marked and how long cats spend marking it.

4. How tracking was or was not used

The study rests on reading one kind of sign: urine marks on plants. Sprayed plants were identified each morning by a strong urine smell or by the typical pattern of dead leaves caused by repeated spraying. No tracks or trailing were used, and the cats were in enclosures.

5. Tracker or observer certification

Not reported. The paper does not say who checked the plants for urine marks or how their identifications were confirmed.

6. Other technologies, skills or innovations

• Jacobs’ selection index, calculated separately for each enclosure, to compare how often each plant species was marked with how common it was.