Have you heard mysterious barking in the dark of the early morning in autumn and winter?
It is most probably a dog-sized male muntjac, calling out to claim a territory, and hoping to attract a mate.
No wonder the slumber of nearby residents to our reserve is often disturbed in the early hours!
Since this dainty little deer first arrived in the county in 1952 (originally from China and then descended from private collection escapees), it has spread quickly, eating its way through undergrowth and spring flowers in woods and town gardens.
Although an island, our nature reserve has its own pair of deer.
They have a fawn in the spring most years, although they may breed year-round.
Here, getting enough food can be an issue.
As muntjac swim well, water isn’t a barrier, and a well-worn track shows that they commute on and off the island, to feed nearby.
Either way, they have taken to the Ouse Valley very well.
With females breeding from 7-8 months old, they have spread rapidly and have few natural predators.
If not heard, one of the first signs of their presence is nibbled bushes and hedges, or neatly trimmed flowers.
As muntjac are small, the ‘browse line’, above which they don’t feed, is usually about 100 cm.
On Holt Island, the deer are elusive during the day, hidden in the undergrowth, although you may be lucky and catch a glimpse of one.
They emerge properly at dusk when visitors are gone.
Our network of trail cameras shows that muntjac use all areas of the island, and gives us the first views of a wobbly-legged fawn.
Normally solitary for much of the year, our deer seem to be social, with the fawn and mother filmed together throughout the summer.
You can see footage on holtisland.org.
The female then gets ready to breed again, and the male defends his territory, and his female, from others nearby.
As well as barking, males will squeal loudly when frightened.
Top tips for sighting: the male has a neat pair of small horns, unlike the female.
Both have white tail covers – usually the only thing seen as they scamper away.