Wildlife - Mammal Surveys


Mammal Surveys

  • Although large, conspicuous mammals are easy to see and count, many species are small and highly secretive, and the surveyor depends on evidence such as tracks and signs. Here are some of the most widely used ways of surveying mammals.
    • Direct count.
    • Line transects.
    • Live trapping.
    • Counting and mapping call.
    • Tracks.
    • Dropping.
    • Feeding remains.
    • Holes are runways.
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Direct Count

  • Conspicuous large mammals such as deer can be surveyed by counting.
  • An area can be gridded or sub-divided into sections and the number of individuals in each section counted.
  • Seals can be counted when they return to land to give birth and bats counted while they roost during daylight.
  • All UK bat species are protected by law (Wildlife Countryside Act 1981) and you need a licence to enter the roost.
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Line Transects

  • This method involves the surveyor travelling along a line, recording the individuals seen on each side.
  • Transects are often carried out from a vehicle or boat which disturbs the animals less than a walker does.
    • Can be taken from further away.
  • They are used for surveying conspicuous species such as deer and marine mammals.
  • Line transects have also been used to survey deer scats (droppings) and they are used in the Winter Mammal Monitoring Survey run jointly by the British Mammal Society and British Trust for Ornithology.
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Live Trapping

  • Used to survey small mammals.
    • Voles, mice, and shrews.
  • The trap that is most used in the UK is the Longworth trap.
    • The trap consists of two parts, the nest-box, and the tunnel with a door at one end and treadle wire at the other.
    • When there is pressure on the treadle wire, the door catch is released, and the animal is trapped.
    • Can increase stress as they are trapped.
    • Easier to catch smaller animals that just using your hands.
  • Hay and food are provided to help the animals survive.
    • Porridge and oats for mice and voles, and tinned pet food for shrews
  • Traps checked twice daily, more often for shrews.
  • Live-trapping is used with mark-release recapture techniques (Lincoln Index) to estimate the population size of varied species.
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  • Some animals are quite vocal, particularly during the breeding season.
    • Including red foxes.
  • Mapping the location of calling animals on repeated visits allows the mapping of  their territories
  • Bat calls:
    • can be surveyed using a bat detector to pick up their echo-location calls. The bat detector by reducing these ultrasonic calls to a frequency that humans can hear.
    • Different bat species produce calls at different frequencies.
    • Similarly, hydrophones are used to record the calls of marine mammals such as whales.
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  • An animal track is an imprint left behind in soil, snow, or mud, or on some other ground surface, by an animal walking across it.
  • Animals tracks are used by hunting in tracking their prey and by naturalists to identify animals living in a given area.
  • Footprints are a useful way of identifying which species are present, their density gives a crude indication of abundance.
  • A tray of sand at a tracking station can provide suitable conditions if the ground is too hard to register tracks.
  • You can make records in the field by sketching the prints in a field notebook or making a plaster cast.
    • Can use plaster of Paris which is available at chemists.
  • Key identification features of prints are its size, its shape and the number of toes.
    • For example, members of the mustelid family are 5-toed and carnivores are 4 toed
    •  Cloven-hoofed animals leave a distinctive track as they only tread on the tips of the third and fourth toes, leaving a symmetrical double mark.
    • Smaller animals are less likely to leave identifiable tracks as they exert less pressure on the ground.
    • Experienced trackers can identify not only species, but also the size of the animal, its gait and the length of time since the animal passed by.
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  • Important aspect of surveying
  • Can tell you not only what animals there are but also their diet
    • Can tell you what other animals are living in the area
  • Many animals have strong distinctive scent, and they are used as territory markers, for example badgers and rabbits, whilst other deposit faeces randomly
  • The form and size of mammal droppings are generally characteristic of species.
  • In using dropping to identify mammals, it’s important to record the shape, size, colour, smell, distribution, and any identifiable content in the faeces.
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Feeding Remains

  • Otter feeding will leave the hard parts of crustaceans, bits of amphibians and the bony parts of fish.
  • Other carnivores often leave remains such as bones and eggshells.
  • Water voles leaves straight lines of clean cut vegetation often near their homes.
  • Hazel dormice leave a smooth, round hole in the side of the nut, with tooth marks running around the inside of the hole.
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  • Can be used to tell what animals are in an area.
  • As a highly social animal, badger setts are large and spacious enough to accommodate as many as 35 individuals.
  • Otters rest in underground dens called holts. They can be up to 10 metres underground and may have underwater entrances.
  • Mature trees particularly those of well-developed root systems, leaning trunks and overhanging branches provide good sites for holts.
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  • Badgers are creatures of habit; they regularly visit the same patches of woodland or open pasture to forage for food.
    • Paths are 10-15cm wide.
    • To create paths, they must follow scented musk trails which they and generations of badgers before them have created.
    • Will stay in the same area and sett for years unless disturbed.
  • Otter mud slides
    • A site along a riverbank used by otters to enter the water may be worn smooth to a form a ‘slide’
    • Sometimes pitted with blurred prints where otters have given it a push for momentum
    • Riverbank slides may be around 8” wide, and much wider with heavy use.
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Feathers, fur and hair

  • Fur and hair can be found in areas where animal have had to squeeze through or go under something, this is usually barbed wire or wood.
  • Fur found on the ground may be a sign of a fight or the remainder of an animal’s meal.
  • Feathers are easy to find, even in towns as birds moult once per year. Feathers may also be left behind after an animal has eaten a bird.
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Reptile Sheds

·   Can tell by the size of the shed for species.

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  • Important not to disturb nesting bird or mammals – it is an offence under the Wildlife and Countryside Act 1981 and even a license is needed for photography.
  • Skylarks are ground-nesting birds that breed from April not early August.
    • Ideal vegetation height is 20-50 centimetres.
  • Hazel dormouse
    • Nest: grapefruit size
    • Found in dense cover, bushes, climbing plants. Also frequently in hollow trees.
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Hair Tubes

  • Used to survey dormice.
  • Lengths of plastic 3cm piping are attached to branches 1 to 2m above the ground.
  • Baited with peanut butter.
  • Double sided sticky tape is stuck to the roof of the tube.
  • Traps are left for 1 to 2 weeks then the tape is examined for hairs.
  • May be difficult to distinguish between hairs if you are unexperienced.
  • Animals may get a little bit stuck to pull hairs out.
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Owl Pellets

  • Consists of things like bones of birds, mammals and fish, teeth, claws and beaks, insect head parts and wing cases.
  • Usually, enclosed by softer material such as fur.
  • Have virtually no smell
  • Pellets are not dropping but are regurgitated by owls as a way of getting rid of the indigestible parts of their food.
  • Normally produce 2 pellets each 24-hour period
  • We can dissect owl pellets to see what the owl has been feeding on.
  • In the 1990s the British Mammal Society carried out a survey on owl pellets.
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Antler Sheds

  • Deer shed their antlers annually.
  • The newly formed antlers are covered in a layer of skin called ‘velvet’ which the deer gets rid of by rubbing or fraying the antlers against thing, springy trees, or bushes.
  • This leaves distinctive damage to the tree bark and side branches may also be broken.
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