behaviour 3

• Methods of capture


  • Cage/ box traps
  • Snares (neck and leghold)
  • Nets (drop, cannon, mist)
  • Pitfall traps
  • Darting
• Capture methods

  • Associated with risks (the trap design, targeting species physiology, capturing non-target species)
  • Risk of causing serious injury, or worse, death
• The majority of these capture methods are not a regulated procedure, and animal welfare biologists think that it is one of the most stressful things that you can do to a wild animal
• The traps etc are designed to restrain the animal no matter how hard it struggles to escape
• You have a legal obligation to check a trap at least once every 24 hours
• If the trap is not checked frequently enough, the animal may die from thirst or hunger, or it might be killed by a predator that also gets captured in the trap
• Catching multiple individuals in one trap can lead to fights and even deaths (this is very common in the capture of rats)
• Trap placement must limit the risk of adverse weather conditions which could lead to hypothermia, sunstroke etc. Also to limit the risk of drowning
• There are now devices that you can attach to traps which are linked to a mobile phone, so it will contact you when the trap is set off
• Most wild animal trapping methods are unselective, so there is always the risk of capturing non-target species
• Capturing non-target species may be protected by the law, it will cause the species lots of stress and may offer significant challenges beyond what you would expect (it might try to kill itself)
• Some species have escape responses that can make them especially vulnerable, even to an approaching human
• Capture myopathy

  The physiological changes associated with a stressful event. It is most often seen in ungulates and carnivores. Capture myopathy is often fatal whilst the animal is confined. However, the damage that is caused sometimes may be just as fatal after the animal is released. The only way to prevent this is to release the animal as soon as it first starts showing signs.
• Another adverse reaction is when it may represent a predictable source of food bait (trap-shyness or trap-happiness). This reaction violates assumptions of equal trap ability.
• Sensory ecology in animal behaviour studies

  Jakob Von Uexkull (1899) - 'All that a subject perceives becomes his perceptual world and all that he does, his effector world. Perceptual and effector worlds together form a closed unit'
• In animal behaviour, the humans views of the world is not the same as an animals view on the world
• Senses (aside from the normal 5)

  • Balance (equilibrioception)
  • Heat (thermoception)
  • Proprioception (closing your eyes and touching your fingers together / nose)
• 6th senses

  • Echolocation (radar) - mainly used in micro-bats
  • Echolocation (sonar)
  • Electroreception
  • Electromagnetism - Migratory birds, turtles and salmon
  • Infrared (body heat)
  • Infrasound - only large species can generate infrasound, however many animals appear to be able to detect infrasound associated with earthquakes
• Eyes

  Designed to detect light, direction, movement, the distance to objects and colour
• Earliest eyes

  Photoreceptor cells that enabled animals to detect light. A positive phototactic response moves towards the light, whereas a negative phototactic response moves away from the light.
• One of the earliest forms of predator detection was once an organism is able to detect light, they were also able to detect movement in the forms of shadows
• Movement

  Works on the concept of the brain receiving multiple sequential signals from which it can then infer movement
• Direction and distance

  We only really need two eyes to detect depth and distance. One eye is able to detect the direction and movement of an object.
• Stereopsis (binocular vision)

  Works on the basis that each eye sees a slightly different image of the same view. The signal from the object to each eye takes a very slightly different amount of time to arrive. The brain uses this complex set of information to estimate the distance to objects and depth.
• Eye structure

  • Cornea - Protects the eye, starts to focus the light
  • Iris - Controls the amount of light entering the eye
  • Lens - Focuses the light onto the fovea of the retina
  • Rods and cones - These are in the retina and absorb the light
• Rods

  Distributed widely across the retina and are very sensitive. They are good for low light levels, but do not generally generate colour vision. They are useful for detecting movement and are mainly for nocturnal animals.
• Cones

  Allow for colour vision and are useful for generating detailed pictures. They have low sensitivity to light, so they are most useful in the daytime.
• Most mammals are dichromatic (red-green blindness), possibly because our early ancestors were nocturnal
• Primates might possibly be trichromatic because our ancestors evolved to eat fruit
• Nocturnal primates have large eyes relative to their size
• Giant squid have an eye about the same size as a football, but they live in the ocean depths where there is no natural light. This is useless for hunting prey but they may use their eyes to detect light caused by (sperm whales) who are hunting using sonar. If they accidentally bump into these animals, it gives them enough time to escape
• Small nocturnal cats have vertical pupils. This allows them to open their pupils much wider than if they were round, this helps to increase their depth perception. However, herbivores living in open habitats often have horizontal pupils to allow them to scan for predators, this means that they would be quite vulnerable to a predator in the sky
• Tapetum lucidum

  Many nocturnal animals have this. It is a layer of cells at the back of the eye that reflects light back through the retina. This creates two opportunities for the photons to be absorbed. This means that the brain is processing information from two images at the same time.
• Critical flicker fusion frequency

  Measures the rate at which the brain processes information. It is the rate (Hz) at which images merge into one continuous stream (like a movie, not as separate images). This also affects the rate at which an animal lives.
• Dogs live at 75Hz, whilst humans live at 60Hz, meaning that for dogs, watching human TV, they would experience it as a series of disjointed images
• Photoperiodism

  Very important in the timing of key seasonal or annual events such as breeding, migration, diapause and hibernation. In mammals this is regulated by the release of melatonin from the pineal gland in response to the length of night.
• Animals can also modify components of their eyes to maximise their fitness, this includes losing their eyes completely if it's too costly for them to maintain them (for example, in subterranean habitats)