Life on the Edge Notes

In: What do you know about Grizzly Bears in Yellowstone National Park?


The Yellowstone Grizzly Bear was listed as ‘threatened’ in 1975 because there were only 136 bears in the Yellowstone area.

Causes of Endangered Species

Invasive Species

Example: Cane Toads in Australia


Rhino horn. Tokay geckos.

Habitat Destruction

  • Palm Oil & Orangutans


Nytimes article

In 2003 there were 9,000 blockbusters worldwide

There is ONLY ONE BLOCKBUSTER LEFT in the wild!

Where? Bend, Oregon.

What has caused it’s near extinction?

The internet. Netflix. Streaming videos.

Why is Bend, Oregon good habitat for Blockbuster?

  • They have slow internet!

Focus on:

Habitat Destruction

Deforestation isn’t the whole story….

Habitat fragmentation is increasing


Habitat fragmentation

Edge Effects Noes


Example of edge effects

Brown-headed cowbirds are brood parasites, meaning they don’t build nests or raise young on their own, but lay their eggs in the nests of other “host” birds.

Cowbird nestlings tend to develop faster and be more aggressive than the host’s nestlings, and as a result, are often the only chick to survive.

Cowbirds prefer edges but will penetrate the forest interior in search of host nests.

With increasing fragmentation, they’ve been able to significantly expand their historic range and, along the way, encounter new and unsuspecting hosts that fail to reject their eggs.

Many avian biologists believe that cowbird

parasitism has led to the declining number

of songbirds in North America.

Not all habitat is created equal

Simple habitat like a manicured lawn is less valuable than complex habitats in terms of its ability to support biodiversity. Even two areas of equally complex habitat can be quite different in terms of their ability to support a given population or species.

Both the size and shape of the habitat area – or patch – affects the richness and abundance of species.

In general, biodiversity decreases as patch area decreases.

Ecologists utilize a number of landscape metrics to evaluate habitat quality and fragmentation; these include patch size, the amount of edge created by these patches and the geometric complexity of the patch shape.

In this activity, we’ll use mean patch size and perimeter-area ratio.

Our most

complex habitat

The most complex habitat on our campus:

= the bioswale

Bioswales are landscape elements designed to concentrate or remove silt and pollution out of runoff water.

A common application is around parking lots, where substantial automotive pollution is collected by the paving and then flushed by rain. The bioswale, or other type of biofilter wraps around the parking lot and treats the runoff before releasing it to the watershed or storm sewer.

Talk to your neighbor. How can you measure the area of each of these patches?

Calculating Patch Size & perimeter/area ratios instructions

Today you will:

-Calculate mean patch area.

-Calculate perimeter-area ratio of habitat.

Problem: Habitat Fragmentation

One solution: National Parks

Case Study: Grizzly Bears and Wolves in Yellowstone National Park

Out: Do you think grizzly bears are habitat specialists or generalists?

Life on the Edge Notes - Google Slides