Ord’s kangaroo rat (Dipodomys ordii) COSEWIC assessment and status report: chapter 13

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Technical Summary

Dipodomys ordii

Range of Occurrence in Canada: Alberta, Saskatchewan

Extent and Area Information

Extent of occurrence (EO) (km²)

EO was based on specimens, live captures, direct observations, and verifiable indirect observations for which the geographic precision was < 8 km. EO was estimated as the sum of the area of two polygons constructed separately in order to exclude a large, intervening area of unsuitable habitat (Figure 3 and Figure 4).

6030 km²

Specify trend in EO

Presumed declining, but at an unknown rate

Are there extreme fluctuations in EO?

Unknown

Area of occupancy (AO) (km²)

AO was estimated according to 250-m wide quadrats (6.25 ha). However this is acknowledged to be a drastic overestimate for the Alberta records, which represent the majority of records. It also weights records in anthropogenic habitats as highly as natural sand dunes, but the majority of anthropogenic sites are not occupied in early spring.

The sum of the potential habitats measured from aerial photos is much smaller, 6.8 km² for more than 50% of the range, and therefore 10 km² is considered a better reflection of occupied habitats.

≤53 km² including anthropogenic habitats (presumed to be population sinks);

ca.10 km² if only natural habitats are considered

Specify trend in AO

Unknown, but assumed to be declining because natural habitats are known to be rapidly declining

Are there extreme fluctuations in AO?

Probably

Number of known or inferred current locations

Each discrete patch of sand hills (Figure 3 and Figure 4) may be considered a separate population and there are multiple locations within each, depending on how many patches of open sand or anthropogenic features there are within each.

>> 10

Specify trend in #

Unknown but presumably declining since natural habitats are known to be declining

Are there extreme fluctuations in number of locations?

Unknown

Specify trend in area, extent or quality of habitat

Area of open sand is declining at a rate of 40% per decade and number of sand dunes declined at 53% in the most recent decade. If this continues, all sand dunes in the Middle Sand Hills are predicted to disappear by 2014.

40 to 53% decline per decade depending on habitat metric

Population Information

Generation time (average age of parents in the population)

<1 year

Number of mature individuals

Two similar estimates by independent data. Confidence intervals:
(i) 560 to 845; and (ii) 545 to 1040.

< 1000 in early spring

Total population trend

Unknown but presumed declining due to known declines in habitat

% decline over the last/next 10 years or 3 generations

Unknown

Are there extreme fluctuations in number of mature individuals?

Yes

Is the total population severely fragmented?

Yes

Specify trend in number of populations

Unknown, although assumed to be declining due to severe habitat loss

Are there extreme fluctuations in number of populations?

No

List populations with number of mature individuals in each:

Unknown

Threats (actual or imminent threats to populations or habitats)

• Loss of natural habitat and habitat degradation through increases in anthropogenic features
• Small population size with severe fluctuations related to anthropogenic influence
• Risks inherent to small populations (e.g., stochasticity, difficulty finding mates)
• Intensive oil and gas development
• Agricultural practices
• Anthropogenic influences that increase botfly parasitism and predation, and interact with foraging behaviour, body condition, and winter severity

Rescue Effect (immigration from an outside source)

Status of outside population(s)?

USA and Mexico: Stable--considered common and widely distributed

Is immigration known or possible?

Not likely

Would immigrants be adapted to survive in Canada?

Not likely

Is there sufficient habitat for immigrants in Canada?

No

Is rescue from outside populations likely?

No

Quantitative Analysis

Not available

Current Status

COSEWIC: Special Concern, April 1995
Endangered, April 2006

Status and Reasons for Designation

Status: Endangered

Alpha-numeric code: A3c; B2ab(iii); C2a(i)

Reasons for Designation: The species requires sand dune habitat, which may disappear over the short term (10 years). The area of occupancy is only about 53 km² and only 1000 or fewer individuals are alive at the end of most winters. There is strong evidence for local adaptations of the Canadian population and a rescue effect is extremely unlikely because the nearest population in the United States is 270 km away.

Applicability of Criteria

Criterion A (Declining Total Population):
Met Endangered, A3c. Inferred from loss of habitat.

Criterion B (Small Distribution, and Decline or Fluctuation):
Met Endangered, B2ab(iii). Based on an area of occupancy of < 53 km².

Criterion C (Small Total Population Size and Decline):
Met C2a(i). Total population size unknown but likely in the thousands. Populations are isolated based on dune habitat, which is declining. Further, high levels of mortality lead to very small numbers of adults in the spring.

Criterion D (Very Small Population or Restricted Distribution):
Number of mature individuals is less than 1000 in early spring. Total population size is unknown but likely in the thousands.

Criterion E (Quantitative Analysis):
Not available.