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Animal Migration Final Exam Review (Case Studies)

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Natural Science
NATS 1550
Alexander Mills

NATS 1550 – ANIMAL MIGRATION FINAL EXAM Case Study #1: Monarch Butterfly - Cannot survive harsh winter: solution – annual migration south in early autumn - Unusual because: southbound adults survive entire winter for return trip Five Generations: - Intergenerational relay: each breeding season, up to 5 generations of butterfly live, reproduce and die in North America - Adults before/ in late summer, have no sex organs - End of August: „obese‟, ready to head South  Long-established routes  „leading lines‟  „stop-start‟ migration  stop for flowers (fat reserves) - Rest in trees  traditional roots; trace the scent of previous generations? - Stop at California to sleep in pines for winter (5 million of them)  Or Mexico‟s volcanic mountain belt (Eastern Monarchs) (100 million) Winter Slumber: - Which sleeping, they don‟t get eaten  they lace their body with toxins  Get the toxins from their main food source, milk weed plants - Wake up around February/ early March - During days, they mate; then head North to lay their eggs; then they die  Adults of this generation = 9 months old (oldest of the butterflies)  Later generations more northward, reoccupying breeding grounds Metamorphosis: - Egg  larva (caterpillar)  pupa (chrysalis)  butterfly (up to 5 generations per year)  Stage 1: 2 weeks to shed skin for growth  Stage 2: 2 weeks to remodel, under the control of hormones  Stage 3: 2 weeks – 9 months to turn into butterfly, depends on season and „role‟ - Same genes as caterpillar/ butterfly  Not all genes operational in birth stages  Hormones trigger  next developmental stage  Dependents: nutrition, time of year - Entire organism changes for new „mode of existence‟  New nervous/ digestive/ reproductive systems Caterpillars - They only eat milkweed; milkweed juice is toxic to most (chems against herbivores)  „glyrosides‟ – charged particles  leads to unbalance in animal cells  Defence against predators; brightly coloured = toxic  Mimics other species (ex. Vicerory Butterflies) - Migration: strongly influenced by north-south landforms: rivers, mountains, coastlines Case Study #2: Red-sided Garter Snake Scientific Name: Thamnophis sirtalis parietalis Migration: to and from hibernation dens Journey length: up to 12.5 miles (20km) each way – or more Where: Narcisse Wildlife Management Area – Manitoba, Canada When: Late April-May Introduction: - Few weeks in spring, largest snake gathering in marshy plains of northwest Canada  Just emerging from their hibernation - Returns in the fall as snakes come back to the den to hibernate - Sleep for 8 months – wake to spend brief summer breeding and feeding  Stop-start existence  only way the cold-blooded can survive extreme Canadian weather  Requires accurate time-keeping, importance of snakes‟ body processes - Main goal not to reproduce but to successfully hibernate Life in the Freezer: - No other American snake this far north near Arctic - Garter snakes produce mild venom – not dangerous for humans - Approx. 50,000 spill into 4 major, and several other smaller dens  These dens caused by 2 environmental factors: (1) Ideal garter snake habitat (ponds/swamps) + favourite prey (frogs) = huge snake pop. (2) Area has high-quality hibernation sites (deep, caves, limestone outcrops) - Herpetologists conducted experiment:  Even when snakes 40% frozen, can still survive  After 10 hours, they will die  meaning their freezing tolerance is short-term  This is meant for early autumn weather, but not for long cruel winter  This is why they must go underground to safely “shut down” - Hibernation is state of regulated hypothermia less heat  Allows animal to conserve energy during winter  Metabolism slows to low level – breathing rates and body temp lowered  Body fat reserved get used up slowly  Period before hibernation when they eat excessively – generate fuel Mating Balls - Mid-April, around 25 degrees C, snakes become action again - Males leave den first, crowd around entrance to mate with female when they leave den - Female snakes are much longer and thicker – males outnumber the females - Orgy – may last a few days or several weeks  depends on weather - Snakes disperse after and hunt for food - Females give birth  10-50 snakelings - First winter will be in scattered burrows, second winter, they will hibernate in traditional dens Home Sweet Home - Homing mechanisms:  Use ability of forked tongue to detect tiny traces of chemicals  Tongue picks up scent molecules from the ground and air – passing them to supersensitive taste receptors in the roof of its mouth  Jacobsen‟s organs  Snake can build a detailed scent map  Detect vibrations through bodies  Thermal clues are also used  Guided by Earth‟s magnetic fields?  Some snakes have been marked and recaptured at the Narcisse den  Majority returns to the same den  A few rotate between different dens  Many unanswered questions:  Where do females give birth and spend summer?  Do they all follow the same routes or disperse and return from all directions - Protagony – females migrate first - Protandry – males migrate first  EELS Case Study #3: Ruby-throated Hummingbird Scientific Name: Archilochus Colubris Migration: From North America to Central American wintering areas Journey Length: up to 3750 miles (6000 km) each way Where to watch: gardens, woodland in eastern North America When: April- July - Their lifestyle depends on flowers – plenty of it, therefore, they must fly south - In spring, it is capable of flying nonstop across the Gulf of Mexico - Most of world‟s approx. 340 species of hummingbirds live in rainforests in Latin America  all year around nectar, rarely leaving forest - Elsewhere, the problem of seasonal nectar supplies - Most except for the long-tailed sylph migrate - Most are strongly migratory Flower Power - Breeds throughout the eastern half of North America  only hummingbird east of Mississippi River - Males – set off a week or two earlier to claim nesting territory - Favourite food plants: cross vine, red buckeye, and firebush – found in Southern USA - Diet: varied, tree sap, spiders, small insects - Mothers raised the young without the males - Growing population produces 2 broods – due to longer summers and bird feeders - Male play small role in migration so they can fly south again - as early as July - Females and young remain in breeding areas until Sept or mid-Oct if weather is not mild enough - They follow variety of routes south  Peak periods – large #s fly in major migration flyways (ex. Mississipi Valley) Dangerous Crossing - Some retrace their route to return north in spring - Some take shortcut across the Caribbean – 700 miles  Too risky during the fall – hurricanes  When it is calm weather: takes the bird 18 hours - One of the longest known nonstop migratory fights of any species of bird - Before the long journey, the birds gather at shores of Yucatan to put on some fat – fuel - Usually double their normal weight - The excess weight used to power the bird‟s huge muscles  All burned out by the time they land in Florida Case Study #4: Red Crabs - Red crabs are an endemic on Christmas Island south of Indonesia (Australian territory) - An endemic species – one that is found nowhere else - Mostly marine organisms  Like other remote islands, Christmas Island is „missing‟ some things  Only 3 native land mammals (2 rats, a shrew), rats are extinct (shrew may be too)  So, it is an ecological niche that is „empty‟ Numerous Species of Land Crabs - Fill the ecological role of small land mammals on the island - Red crabs are the dominant ones  Dig burrows, fertilize the soil, recycle nutrients by eating vegetation  Even influences forest structure by eating seeds and seedlings - Abundant (millions) of Yellow Crazy Ants (West Africa)  Spends most of their lives in forests – then returns to sea to breed Crabs Synchronized by Weather and the Moon 1) Weather: Indian Ocean Monsoon: period of excessive rain; early Nov.  Crabs begin moving down from the forest plateau towards the coast  Taking a week and more than a km per day  Signs warning cars of Red Crab migration, no access to roads  In some areas, bar
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