The Harvest Mouse
Harvest Mice in Owl Pellets and Tennis Balls
1 Discovery and Context
2 Micromys - Description
3 That Wonderful Procreant Cradle
4 Where Are They Now?
5 Deaths and Entrances
6 Keeping Harvest Mice as Pets
Harvest Mice in Pellets.
Anyone for Tennis (Balls!).
Owls swallow their prey items whole rather than tear off the juiciest pieces as falcons and hawks do. The indigestible bits; fur, feathers and bones are regurgitated as a “pellet”.
They are produced wherever the owl happens to be at the time but as they are creatures of habit, roosting at regular places until they fall out of favour, the pellets can be found, sometimes aplenty, beneath where they were perched.
They are not at all like poo; they don’t smell and they are dry. They are oval-shaped and they spent some time in an owl’s stomach but there the resemblance ends for they have not been digested at all and the contents are really interesting and reveal a lot about what the owl had been eating and therefore something about the creatures that formed their prey.
Kestrels and other Sparrowhawks do produce pellets because inevitably some fur and feathers gets swallowed along with the vole and the sparrow flesh but they are fewer in number and not so interesting.
Little Owl pellets often contain black shiny flecks of beetle elytra along with bits of worm and grass.
Tawny Owl pellets are 4-6cm long and grey with a rather irregular surface. Tawny owls tend to be woodland species so from a Harvest Mouse perspective they are not of interest here.
Barn Owl pellets are shiny and blackish when fresh regardless of what they have been eating but they turn grey as they age. They are 2.5 to 3.5cm long and usually cylindrical with domed ends but some are shorter and nearly spherical.
There is plenty of information on how to find, dissect and identify prey items on other sites such as this one on the Barn Owl Trust's site, though it doesn't have any information on Harvest Mice, or this one at the RSPB, which does. (Both open in new windows).
Harvest Mice in Pellets.
Harvest Mice do not normally form a significant part of the Barn Owl's diet. In a recent study in Suffolk, 36% of 223 sites that had Barn Owl pellets had Harvest Mice remains but this was just 1.4% of total prey items (and even less as biomass).1 Although nationally they are found in 0.8% of Barn Owl pellets, in Sussex this figure was as high as 65% in November though it had dropped to less than 1% in June/July.
Nevertheless, Harvest Mouse remains are another indication of the presence (though not necessarily the absence) of Harvest Mice in a study area and there is much to be learned about the correlation of the occurence of Harvest Mice remains and the vole and shrew populations.
Harvest Mouse skeletons are fragile and a spell being ground around in a Barn Owl's gizzard takes it toll but the jaws are usually complete and they are all that is needed to identify any small mammal. There is information elsewhere on the identification of small mammals, as in the links given above but Harvest Mice molar rows are short at less than 3mm and the 1st lower molar has 3 roots, rather than 2 in the other British mice whilst the equivalent molar in the upper jaw has five roots where the Wood Mouse normally has four and the House Mouse has three.
1. Meek and Bullion; Can the Harvest Mouse survive in a modern arable landscape? A Suffolk case study. British Wildlife magazine Vol 23 Nr 6 pp419:423.
Harvest Mice can be trapped in small mammal traps such as Longworths. Traps at ground level put out for mice and voles may occasionally trap harvest mice but in reed beds they are best situated some distance above ground level. This can be achieved by taping the trap to a garden cane. Please be fully conversant with the good practices of live trapping mammals before attempting it.
This is another method of detecting the presence of small mammals...........More to come
Anyone for Tennis (Balls!).
Some years ago, there was masses of publicity about the Wimbledon tennis tournament recycling its used tennis balls to provide homes for the threatened Harvest Mouse. Apparently some experimentation had shown that Harvest Mice will adopt tennis balls, if a suitably sized hole is made in them and they are placed on sticks in nice grassland.
I've tried this with my captive mice and they do enter the ball and bring in some hay to make it more comfortable though they seem to prefer the woven willow balls if an entrance is made, and they obviously only use it for resting. It's intuitively obvious that they couldn't use a tennis ball as a nest because it wouldn't expand to accomodate the brood and would completely counter the mouse's instinct a) to build a nest, and b) to build it in a location that the mouse thought was safest.
Needless to say, the project failed disastrously, though the publicity about this was less than on its launch and there seems to be a consensus among the general public that tennis balls make suitable substitute nests for Harvest Mice.
Small is Beautiful.
An ITV film broadcast in 1980 in the Junior Survival series. The farming is very out of date (sadly in most cases) but otherwise the film is informative.