Data Deficient

What "Data Deficient" means

Data Deficient is a label on the IUCN Red List, the global inventory of extinction risk run by the International Union for Conservation of Nature.

A species is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution or population. Its official abbreviation is DD.

Data Deficient is not a threat category. It doesn't say a species is safe, and it doesn't say a species is in danger. It says the evidence isn't there yet.

Why a species ends up Data Deficient

It isn't always because a species is obscure. IUCN notes that a Data Deficient species may be well studied, with well-known biology, while still lacking the data on numbers and range that the Red List criteria need. Common reasons include:

• Remote or hard-to-survey habitat, such as deep oceans, dense rainforest or underground.
• Few recent records, so nobody knows whether the population is growing or shrinking.
• Unsettled taxonomy. If one "species" may actually be several, nobody can say how big each population is. That's why the orca is listed as Data Deficient.

How it compares to other categories

Data Deficient sits outside the Red List's risk scale:

• Not Evaluated (NE): never assessed.
• Data Deficient (DD): assessed, but there isn't enough data to place it.
• Least Concern through Critically Endangered: assessed and placed on the scale.

IUCN cautions assessors against using Data Deficient when a lack of records might itself be a warning sign. If a species has a small range and hasn't been seen in a long time, a threatened category may be more appropriate. Once better information comes in, a Data Deficient species can be reassessed and placed in any category, including a threatened one.

Data Deficient vs. U.S. law

Data Deficient has no legal meaning in the U.S. The Endangered Species Act is a separate system, so a species can be Data Deficient on the Red List and still have legal protections, or none at all.

Data Deficient animals at the zoo

You'll occasionally see a Data Deficient species at a zoo, such as the black tree monitor. Animals in human care can help fill gaps in knowledge: records on breeding, growth, lifespan and behavior give field researchers a useful baseline for species that are hard to study in the wild.