Scat analysis reveals a wide set of plant species to be potentially dispersed by foxes

1. What they did

Seeds need help to travel, and animals are among the most important carriers. Birds and plant-eating mammals are well known seed dispersers, but meat-eating mammals often eat fleshy fruit too. In Flanders, Belgium, the most common wild predator is the red fox. Foxes eat almost anything, live in many kinds of landscape, move several kilometres a day within their territories, and young foxes travel 20 to 40 km in autumn looking for new territories. The authors asked which plant species foxes might be spreading in their scats.

• Collecting scats. They used 303 fox scats from all over Flanders: 246 collected in 2004 to 2005 by government nature agency staff for a study of a fox tapeworm, and 57 collected by volunteers in 2008 to 2009.
• Making them safe. Because foxes can carry tapeworms, the scats were frozen at -80°C for at least seven days and then stored at -20°C.
• Finding the seeds. Each scat was soaked in water and sieved through a fine mesh (355 µm). Every seed, fruit or seed-like part was picked out, dried and identified under a microscope, using a seed atlas and Ghent University’s seed collection.

2. What they found

How many seeds

• 5207 seeds in total, in 172 of the 303 scats (57%).
• Most scats with seeds held fewer than 10. One September scat held 1135 seeds, 993 of them from brambles (Rubus).
• All but 11 seeds were identified, mostly to species or genus: 77 plant taxa in all.

Which plants

• Woody plants with fleshy fruits (berries and drupes): 82% of the seeds. Brambles (Rubus) alone made up 64%. Others included hawthorn, cherries and plums, apple, rose, elder and yew.
• Woody plants with dry fruits: birch was in more scats than any other plant (23% of scats), though usually in small numbers (up to 37 seeds per scat). Alder, conifers, willow and ash also turned up.
• Herbs and grasses: many species, including wheat, goosefoot, knotweed and grasses, and crop or birdseed plants such as millet, canary grass, sunflower, flax and sesame.
• Some came from wild plants, others from cultivated plants, garden escapes or waste (for example grape seeds in a March scat).

When

Autumn scats held seeds more often, and more seeds, than spring scats. On average, September scats held the most.

3. What they concluded

• The wide range of plants in fox scats reflects the foxes’ opportunistic diet, with many seeds coming from people’s crops, gardens and waste.
• Fleshy fruits are eaten for their sugars and fats. Low-growing brambles are probably eaten straight from the plant; fruit from taller shrubs and trees is probably eaten after it falls, although foxes may also take it from low branches.
• Most dry-fruited seeds were probably swallowed by accident: with grass leaves that foxes sometimes eat to aid digestion, inside or on prey, or in waste (sesame is common on bread rolls). Millet, canary grass, foxtail millet and wheat, found together in one scat, almost certainly came from caged birds or poultry that the fox had eaten.
• Because foxes are widespread and mobile, they could carry seeds at local and regional scales. But whether they are effective seed dispersers still needs study: the authors could not test whether the seeds were still alive (freezing and storage may have killed them), and whether seeds grow from scats in the field is little known.

4. How tracking was or was not used

The scats were found and identified as fox scats in the field by agency staff and volunteers. The authors state that fox scats are easily told apart from those of other carnivores, citing a Dutch field guide to animal tracks and signs (van Diepenbeek 1999), and that foxes often leave them on raised spots such as grass tussocks or tree stumps, at boundaries such as paths and ditches, as scent marks. No other check of the identifications (such as DNA) is reported. The study then analysed the contents of the scats.

5. Tracker or observer certification

Not reported. The scats were collected by staff of the Agency for Nature and Forest, Natuurpunt and other volunteers; nothing is said about their skill in identifying scats. The results assume all 303 scats were from red foxes.

6. Other technologies, skills or innovations

• Seed identification under a stereomicroscope with a seed atlas and a reference seed collection.
• Reuse of scats first collected for a tapeworm study.
• Deep freezing at -80°C to kill tapeworm eggs before handling.

7. Implications for conservation (from the paper)

• Seed dispersal, and long-distance dispersal in particular, matters for the spread of invasive plants and for plants surviving in fragmented landscapes.
• Foxes may carry seeds of both native and non-native plants (for example blackthorn and the alien black cherry), but their real role as seed dispersers still needs to be tested.