Limits and Constraints on Behaviour - Presentation #3 - PDF

Limits on behaviour, and how to push the boundaries Behavioural Ecology Presentation #3: Focus on pushing abiotic limits Limits are related to trade-off analysis ASJf; f F f...

Limits on behaviour, and how to push the boundaries Behavioural Ecology Presentation #3: Focus on pushing abiotic limits Limits are related to trade-off analysis ASJf; f F f This is to exemplify a point: Organisms can occupy different places along the line, but all organisms must stay on the line. We might have different axis labels and yet have the same constraint. All behaviours operate within limits Trade-offs are a necessity Abiotic factors, e.g. This talk focuses on the abiotic ones. Temperature And, we consider ways limits are pH extended by behavioural adaptations. Water conditions Biotic factors Biotic threats Biotic opportunities Biotic partners History Developmental Evolutionary Thermoregulatory Behaviour: Many motivated behaviours Temperature and animal performance - 1 Often “mediated” by enzyme performance Enzyme performance is related to shape and to flexibility, and these vary with temperature Testing for the optimal temperature range Affinity of an enzyme for its substrate is a measure of its performance If substrate concentration is low, the enzyme is performing well This is because the enzyme has a high affinity for the substrate Acetylcholinesterase in Rainbow Trout Acetylcholine is a neurotransmitter that needs to be broken down to “turn off” neurons for proper neural function Two forms of acetylcholinesterase in Rainbow Trout One has highest affinity for acetylcholine at 2oC = winter temperatures Affinity declines rapidly about 10oC The other has highest affinity for acetylcholine at 17 oC = summer temperatures Affinity declines at both higher and lower temperatures Behavioural responses: seek cover in heat or adjust depth to find optimum Rainbow Trout do not do well in “warm” water (e.g. above about 23oC): poor swimming efficiency a At the individual level, Ta represents the temperature an individual is acclimated to in a laboratory experiment, and CTmax is the temperature coinciding with death or loss of critical functions. b At the population level, Topt is the temperature of highest abundance in the wild, and Tlim is the 95th percentile of maximum temperatures encountered by that species in its natural range. Temperature and animal performance - 2 Often “mediated” by water balance challenges Some obvious behavioural responses… Two ways to have lots of water: conservation (like here), and acquisition Temperature and animal performance - 2 Often “mediated” by water balance challenges High temperatures often require a liberal supply of water to keep temperatures down Evaporative cooling is one solution Water changes from a liquid to a gas, and this phase change absorbs heat The organism giving up the water experiences a net cooling effect Consider Deserts and water challenge Water acquisition and Water conservation Needed for usual metabolic purposes, but also for thermoregulation Apache Cicada: Diceroprocta apache These can remain active when ambient temperatures exceed lethal temperatures: How? Need water: feed on xylem Diverse behavioural adaptations Two ways to have lots of water: conservation and acquisition (like here). Endothermy and ectothermy have great implications for behaviour Ectotherms primarily rely on external sources of heat Endotherms primarily rely on internal sources of heat Endothermy can greatly increase the behaviourally acceptable ambient temperature range So, phylogenetic history impacts behavioural opportunities Endotherms and temperature Thermal neutral zone (TMZ): the range of temperatures over which the metabolic rate of the animal does not change RMR: Routine metabolic rate for ectotherms Tr is routine temperature MMR: Maximum metabolic rate for endotherms BMR: Basal metabolic rate TNZ: Thermo-neutral Zone Fence Lizards in the e. USA Sceloporus undulatus Use movement to achieve ~33 oC body temperature as much as possible In-between states: Some moths are endothermic, but not homeothermic Phenotypic plasticity: Clear- winged Grasshopper Colour allows organism to increase radiative heat gain (darker) or to decrease radiative heat gain (lighter) An example of phenotypic plasticity (morphology) that facilitates a behavioural pattern of thermoregulation. Clear-winged Grasshopper These may have a different reason to elevate their temperature to their ideal – which is ~39oC. The devastating Entomophaga grylli fungus thrives at 30oC but dies off at 35oC. Pushing limits: Namib Sand-diving Lizard Solution #1. Alternate raising feet off hot sand Solution #2. Dive beneath the sand to get cooler Another solution is to shut down Obligate, for the winter → hibernation Ectothermic Wood Endothermic Frog, guarded from Eastern death by Chipmunk cryoprotectants. Facultative, for the night →torpor  Composite infrared images of a Blue-throated Torpor Mountain-gem Hummingbird in normal sleep state, transitioning to torpor, then in torpor.  Hibernation From the Latin meaning to pass the winter But some tropical species hibernate when there is a food shortage for a reason other than cold The Fat-tailed Dwarf Lemur hibernates for about 7 months per year. The fruits and flowers they eat are too scarce in the long dry season. Also, pH change can cause molecular changes to olfactory cues