Unusual findings on host-tick interactions through carnivore scat analysis

1. What they did

Ticks carry diseases that harm livestock, people and wildlife, so it helps to know which ticks live on which animals. The usual way to find out is to catch the animals, or examine dead ones, and pick off the ticks. That takes time and money and is hard with rare or protected species.

While studying the diet of red foxes and common genets in Sintra-Cascais Natural Park, Portugal, the researchers noticed ticks among the food remains in the scats. They set out to show that predator scats could reveal which ticks live on the prey the predators eat.

• Collecting scats (November 1994 to September 1995). Fox scats were collected along road transects and genet scats at latrines, each visited every two weeks: 352 fox and 588 genet scats in all.
• Analysing the scats. Undigested prey remains (bones, teeth, hair, feathers, scales, seeds, shells and insect parts) were separated and identified to species where possible. Ticks found among them were kept in alcohol and identified with standard keys.
• Linking ticks to prey. For scats that held the remains of just one prey species, they matched each tick to that prey animal.

2. What they found

Diet

• They identified 523 prey items in fox scats and 1922 in genet scats; most were mammals (66% for the fox, 58% for the genet). Lagomorphs made up 60% of fox prey items; rodents made up 42% of genet prey items.

Ticks

• 276 partly digested adult ticks of six species were found.
• More came from genet scats (186) than fox scats (90), but per scat there was no difference between the two predators.
• About 7.6% of scats held ticks, for both predators. Scats held up to 15 ticks (fox) and 12 (genet), with an average of about 4 per infested scat.
• Rhipicephalus pusillus made up 93% of all ticks (84% in fox scats, 98% in genet scats). The numbers of male and female ticks did not differ.
• Ticks turned up mostly from April to July, peaking in May to July, with a few in January to March and September.

Which ticks went with which prey

• Ixodes acuminatus and Ixodes ricinus were found (in the text) only in scats from meals of wood mice. The authors call the wood mouse link for I. acuminatus a potential new host-tick interaction for Portugal.
• Ixodes hexagonus and Ixodes ventalloi were found in scats from meals of wild rabbits only.
• Rhipicephalus pusillus was the least choosy, found with most of the mammal prey (rabbits, wood mice, water voles, rats, mice and dormice), but mostly with rabbits.
• Rhipicephalus turanicus with a vole (Microtus sp.) was the first such record for Portugal.
• All six tick species were already known in Portugal, but these were the first records for the study area.

Where the ticks came from

The ticks could have come from the predators grooming themselves, or from the prey they ate. The authors think they were the prey’s ticks: earlier diet studies of carnivores in western Portugal found no ticks in scats, no fur from self-grooming was found in these scats, and carnivores usually swallow prey in large pieces, so the prey’s ticks would tend to stay unbroken. For the vole and R. turanicus and the wood mouse and I. ricinus links, they could not rule out grooming, because genets also host both ticks in Portugal.

3. What they concluded

• Scats are a new source of biological information, and scat analysis is a good complement to the usual methods for studying which ticks use which hosts.
• The tick prevalence is probably an underestimate: no larvae or nymphs were found, likely because these small, soft stages are digested or missed with standard scat methods.
• Because predators tend to catch weak or sick prey, the ticks in scats may give a biased picture, but one that widens the view of the tick communities on the prey.
• With small samples, several links are only indicative and need confirming.
• The method works best when adult ticks are abundant (in Portugal, the warmest months) and when mammals make up most of the predators’ diet.

4. How tracking was or was not used

Signs, not trailing: the study rests on scats. Fox scats were collected along road transects and genet scats at latrines, using what the authors describe as differences in the two species’ marking behaviour. The paper does not say how scats were attributed to fox or genet. In the laboratory, prey were identified from remains in the scats (hair, bones, teeth, feathers, scales and other parts).

5. Tracker or observer certification

Not reported. The paper does not say who found and identified the scats in the field, or how they were told apart. The tick findings depend on correct attribution of scats to fox or genet.

6. Other technologies, skills or innovations

• Using ticks found in predator scats, matched to single-prey meals, to infer which ticks the prey carried.
• Identifying ticks with standard taxonomic keys after storage in alcohol.

7. Implications for conservation (from the paper)

• Ticks spread diseases that cause death and distress in livestock, people and wildlife, so knowing the tick community of each animal helps predict and reduce their impact.
• Catching hosts is costly and hard for low-density or protected species; scat analysis offers a complementary, indirect way to study their ticks.