Ecology- Unit 3 Flashcards
Ecology’s Primary Rule
We can never do just one thing.
Even when we think we’re just doing one thing, we’re actually doing a whole bunch of things.
For every action there are multiple reactions.
Yangtze River Dolphin
Most endangered of all river dolphins, habitat limited to just one river. Poor eyesight, relies on sonar and touch.
Illegally hunted partially for medicinal use.
20/20 Hindsight
We generally understand the relevant interactions better AFTER we’ve seen them all play out.
We often don’t know what we did until after we see what happens.
Example of ecology’s primary rule in introduction
Intentional species introduction- game fish in Africa, rabbits in Australia). Rabbits overpopulated marsupials and wrecked ecosystem.
Example of primary rule reduction
Grey Wolfs
-Native to Yellowstone when park was established.
-By 1940 sightings was rare, in 1970 no evidence at all. Only remained in Minnesota and Michigan Isle.
- Reduced by reliance on technological innovations.
-subject to predator control- traps, poisoning, shooting. Before, wolves were way harder to catch.
-traditional trap was a hole with bait on middle pole, wolf would walk on to.
- Bear traps cost 150, rifles are still much less expensive, more accurate, and portable.
-Much more poisions than we used to, pesticides
-Wolves returned in 1996
Why were wolves removed?
Eliminate large predators to protect domestic animals and reserve wild prey species for human hunters. Aldo Leopold found out it didn’t work this way
Pre and post 1996 Yellowstone for elk
Before wolf reintroduction, elk preferred river valleys where their grazing stopped tree growth.
After, elk avoid river valley since they could be easily hunted and since no grazing tree, beaver, and wetlands rebound.
indirect effects of wolf removal
Changes in elk grazing, changes in tree cover, reduced beaver and trout populations due to habitat destruction. No beavers reduced wetland quantity and quality. (can’t stop drought, flood, water pollution).
Wolves hostile to coyotes, after eradication coyote population skyrocket. Coyotes are generally hostile to foxes. As more foxes died, the prey abundances went up.
