2 Orientation movements 1. Simple responses to immediate surroundings = kineses and taxes and have an immediate benefit e.g. a slater moving into a damper place.
3 2. Complex movements over long distances to a pre-determined location which is out of direct sensory contact e.g. migration and homing which are internally initiated.
4 Environmental Stimuli A slater retreating to a daytime crevice could be responding to the dampness, darkness or coolness.
5 Choice chambers are often used to identify which stimuli influence their behaviour. This is a fair test where all factors are kept the same except for the one factor being investigated.
6 For a humidity investigation water is placed in one chamber and a drying agent such as silica gel is placed in the other chamber. Left for 20 minutes, the number in each chamber is statistically analysed.
7 Simple orientation mechanisms Taxis = movement of an organism towards or away from a stimulus.
8 Positive = towards Negative = away Negative phototaxis = movement away from light e.g. earthworms Positive phototaxis = movement towards the light e.g. many swimming algae
9 The direction of the light source is indicated by white rectangles. Phototaxis, Dictyostelium giganteum (A Cellular Slime Mold )
10 Positive chemotaxis = movement towards a chemical source e.g. mosquitoes towards people along CO 2 gradient When a capillary tube filled with glucose is placed in a medium containing E. coli, the bacteria alter their locomotion so that they congregate near the opening of the tube.E. coli
11 Positive rheotaxis = movement against a current e.g. salmon
13 What does an animal do when it has a specific need, such as food, a higher humidity environment, or shelter from the sun, but it has no information about the location of the needed resource? It may engage in an undirected search, or kinesis. Kinesis = random movement due to the presence of a stimulus. The rate of activity is determined by the intensity of the stimulus – not the direction
16 This simple diagram illustrates the basics of an undirected search. The animal, travelling from left to right in the diagram, moves in a more or less straight line through unsuitable habitat. When it begins to perceive better conditions (the blue area) two things can change--its rate of speed and the angle of its turns. By turning sharper angles and slowing down, it stays in the vicinity of the improved conditions. Simple changes in movement pattern, in response to better environmental conditions, amount to habitat selection. Conversely, if an animal finds itself in poor conditions, rapid, straightline movements will increase its likelihood of finding better conditions.
17 Two types: Orthokinesis = stimulus intensity determines speed of movement e.g. slater’s rate of movement is inversely proportional to the humidity Klinokinesis = stimulus intensity determines rate of turning eg lice turn more often in 35° than in 30°. Human skin temp is about 35°. lice more likely to return to, and stay longer in, 35°. Orthokinesis and klinokinesis movies
18 Migration = an active, regularly repeated movement in a particular direction by a population of animals
20 Excludes passive dispersal (carried by the wind). Usually to a feeding and/or breeding area. Usually a two-way trip. Usually have regular timing. Often over long distances. Often at a definite life-cycle stage
21 Examples Salmon – feed at sea and migrate up rivers to spawn. Swim up same river in which they hatched – find natal stream by its unique chemical properties.
23 Eels and whitebait swim downstream to spawn. Young swim upriver to feed and mature.
24 Zooplankton twice-daily migrate 1000m vertically to feed at night and gain protection of depths during the day
25 Vertical Migration Many freshwater and marine zooplankton perform daily excursions (i.e., vertical migrations) up and down in the water column, with changing levels of light triggering these daily migrations. For example, the classic pattern consists of zooplankton residing deep in the water column during the day when light levels are high. They ascend at dusk to the surface waters where they graze on phytoplankton at night. Then, at dawn, they descend and the daily cycle of vertical migration begins again. This behaviour most likely evolved as an anti predator strategy. The major predator of zooplankton is planktivorous fish (e.g., perch, alewives, or mackerel in the ocean). Most planktivorous fish are visual feeders and require a certain light intensity for efficient feeding. So zooplankton avoid becoming dinner for fish by remaining in deep dark waters during the day, and ascending into dark, food-rich waters at night.
26 When to migrate? Need to know time – usually daylength measured by an internal clock Wilson’s Plover
27 Homing = the ability of an animal to find its way home over unfamiliar territory. Not necessarily distinct from migration i.e. salmon might be homing on natal stream
28 Examples Albatrosses wander thousands of kilometres of Southern Oceans and return every two years to NZ to breed.
29 Limpets return to the same spot on a rock before low tide.
30 Ecological significance of migration Migration costs energy and runs risk of getting lost Advantages include longer feeding time, safer breeding area, reduce intra-specific competition, kill parasites
31 How animals find their way Some learn by moving with older ones. But, a shining cuckoo can fly 4000km from NZ to Solomon Islands without ever meeting its own sp. behaviour must be innate
32 An animal must have: a sense of direction (some form of compass) a sense of location (understand where it is starting from) "Well according to the Global Positioning System we are exactly in the middle of nowhere."
33 Animal compasses To find out if an animal uses a particular cue it is eliminated by blocking off the sense used to detect it i.e. light – cover eyes/use mirrors
34 Many migratory birds have a sun compass Must allow for the apparent movement of sun during the day – i.e. needs to know ‘the time of day’ Sun compasses
35 Seasons Summer sun Winter sun
36 Birds have a highly developed sun compass. At the time of migration, a caged bird tends to orientate itself in the direction of migration.
37 When mirrors changed the direction of the light, birds orientated themselves relative to the reflected sun’s rays.
38 10am Direction of migration 90°
39 3pm Direction of migration 180°
40 10am Direction of migration 90° mirror
41 When their internal clock was delayed, the birds orientated themselves relative to their perceived time – not to the actual time.
42 Actual time 3pm Direction of migration 90° ‘Bird time’ 10am
43 -the Sun is not always visible So many birds and insects can see UV light which passes through clouds. Bees, fish and whales can even detect polarised light Disadvantage of a solar compass
44 Migration movements on an overcast day.
45 Star compasses Birds caged in a planetarium showed a strong tendency to move in the direction of their normal migration. When the planetarium sky was rotated 180° the birds direction also reversed.
48 The key feature is the Celestial Poles. No internal clock needed because the direction of the Celestial Pole does not change
50 Moon compass Sandhoppers move towards the sea using the moon’s position and an internal clock to compensate for moon’s apparent movement
51 Using earth’s magnetic field Many animals can sense Earth’s magnetic field. On an overcast day the homing ability of pigeons with magnets on their heads was impaired yet those with brass rods were unaffected A chain of magnetic particles is visible inside this bacterium. This simple compass keeps the microscopic organisms always swimming north.
52 On sunny days bar magnets made no difference. So solar compass normally takes priority. The influence of magnetism on pigeon homing. Pigeons were released with either a magnet or a brass bar of the same weight on their back. On sunny days, the pigeons used the sun as a compass and homed accurately with or without a magnet. However, on cloudy days, the magnets disorientated the birds. Each dot represents the birds vanishing direction. (Modified from Keeton, 1971)
53 On sunny days bar magnets made no difference. So solar compass normally takes priority. The influence of magnetism on pigeon homing. Pigeons were released with either a magnet or a brass bar of the same weight on their back. On sunny days, the pigeons used the sun as a compass and homed accurately with or without a magnet. However, on cloudy days, the magnets disorientated the birds. Each dot represents the birds vanishing direction. (Modified from Keeton, 1971)
54 A primary compass one compass = greater accuracy. Sun and star compasses used when possible with magnetic when it is cloudy. Pigeons with magnets navigated better on sunny days than pigeons without on cloudy days Sun very important as a compass
55 But birds unable to see the sun as they develop could not navigate by sunlight but could on cloudy days magnetic compasses are inborn while using the sun and stars is learned.
56 Besides compasses some animals use environmental cues such as chemical characteristics (salmon) and infra-sound of surf or wind
57 Experience Plays an important part. Migrating birds caught and shifted. Experienced birds corrected error. Juvenile birds continue in displaced direction some birds seem to have an innate sense of directionbut the ‘map’ needed for navigation has to be learned.