Mammal field guide · Mustelids

Photographing the American Ermine

How to photograph the American Ermine (Mustela richardsonii): the right lens for its size, shutter speeds for perched and moving animals, and when it's most often seen (May, June, July and August).

20–130 cm1/2000 s
American Ermine (Mustela richardsonii)
Photo: © Christian Back, some rights reserved (CC BY), uploaded by Christian Back via iNaturalist
20–130 cm
Typical length (family range)
1/800 s
Shutter: perched / still
1/2000 s
Shutter: action / flight
f/5.6–f/8
Aperture
3,133
Research-grade sightings in N. America
ModeManual + Auto ISOLock shutter & aperture, let ISO float
Shutter (still)1/800 s
Shutter (action)1/2000 s
Aperturef/5.6–f/8
FocusAF-C + subject/eye detectionGet down to eye level; a long lens with close focus (or an extension tube) helps with small subjects.
DriveHigh-speed burst
Lens100–400 mmFull-frame equivalent

Focal length needed to frame it#

For a subject about 75 cm long filling a third or half of the frame width horizontally.

Distance⅓ of frame (FF)½ of frame (FF)⅓ of frame (APS-C)⅓ of frame (MFT)
5 m (16 ft)78 mm117 mm52 mm39 mm
10 m (33 ft)156 mm234 mm104 mm78 mm
15 m (49 ft)234 mm352 mm156 mm117 mm
20 m (66 ft)312 mm469 mm208 mm156 mm
30 m (98 ft)468 mm703 mm312 mm234 mm
50 m (164 ft)780 mm1,172 mm520 mm390 mm

When to find it#

Jan: 7% Jan Feb: 6% Feb Mar: 6% Mar Apr: 6% Apr May: 12% May Jun: 10% Jun Jul: 12% Jul Aug: 11% Aug Sep: 9% Sep Oct: 6% Oct Nov: 6% Nov Dec: 7% Dec
Share of iNaturalist observations by month across North America. Peak months: May, June, July and August.

About the American Ermine#

The American ermine or short-tailed weasel (Mustela richardsonii) is a species of mustelid native to most of North America.

Summary adapted from Wikipedia via iNaturalist (CC BY-SA 4.0).

Field-craft tips#

  • River otters play at the same haul-out spots daily.
  • Get down to eye level; a long lens with close focus (or an extension tube) helps with small subjects.
  • Sightings peak in May, June, July and August, which is when you'll have the most chances.

Ethics#

  • The welfare of the animal comes first: if it changes its behaviour because of you, you are too close.
  • Stay on trails, respect closures around nests, leks, dens and haul-outs.
  • Avoid playback and baiting in sensitive seasons; never bait predators.
  • Don't share precise locations of rare, nesting or roosting animals publicly.

More Mustelids#

North American River Otter North American River OtterLontra canadensis American Mink American MinkNeogale vison Sea Otter Sea OtterEnhydra lutris American BadgerTaxidea taxus Long-tailed Weasel Long-tailed WeaselNeogale frenata FisherPekania pennanti American Marten American MartenMartes americana

Frequently asked questions#

What lens do I need to photograph an American Ermine?

At about 75 cm long, an american ermine fills a third of a full-frame image at 10 m with roughly 156 mm, or at 20 m with 312 mm.

What shutter speed should I use for an American Ermine?

1/800 s when it's still; 1/2000 s for action.

When is the best time to photograph a American Ermine?

Observations in North America peak in May, June, July and August. Early morning and late afternoon give the best light and activity.

Sources & licences#

Last updated October 03, 2026 · How we calculate · Sources