Maja Hampson's Zoo Keeping Adventures

Some of you may have heard of animals referred to as “critically endangered” or “vulnerable.” But what does that really mean? Where do these statuses come from?

The IUCN has a “Redlist of Threatened Species” which is where the official classifications of species comes from. Species are classified in this way:

But what's the real difference between a critically endangered animal and a vulnerable one? Well I'm glad you asked. Animals are categorized based on:

1. Population decline
   
2. Geographic range
   
3. Population size
   
4. Number of mature individuals
   
5. Probability of extinction
   

There are more specific subcategories within all these but we won't get into that today. Here is a comparison between critically endangered and vulnerable species:

	Critically Endangered	Vulnerable
Population decline	Reduction of more than 90% over the last 10 years or three generations	Reduction of more than 50% over the last 10 years or three generations
Geographic range	Occurrence = less than 100 km2	Occurrence = less than 20,000 km2
Population size	Less than 250 individuals	Less than 10,000 individuals
Number of mature individuals	Less than 50 mature individuals	Less than 1000 mature individuals
Probability of extinction	Probability of extinction in the wild = 50% within 10 years or three generations	Probability of extinction in the wild = 10% within 100 years

As you can see, species with a much smaller range, population size and a much higher chance of extinction are classified as critically endangered. Many species remain to be evaluated because doing in-depth analysis of species requires time and resources.

Hopefully I've helped you understand the these terms! You can look into the statuses of local animals in your community by visiting the IUCN Redlist.

Hippo (Hippopotamus amphibius) - Vulnerable