World Otter Day 2027 is on Wednesday, May 26, 2027. The International Otter Survival Fund holds it on the last Wednesday of May each year to raise awareness of the world’s otter species and the threats they face.
World Otter Day 2027 is the 12th edition of the observance, which the International Otter Survival Fund (IOSF) launched in 2016. Unlike most awareness days, it has no fixed date.
It falls on the last Wednesday of May, so the date shifts between May 25 and May 31 each year. Calendars that list a single date such as “May 27” are only correct for that year. By 2023, 40 countries marked the day on every continent except Antarctica.
This page gives the dates from 2027 to 2031, the conservation status of every otter species, the trade rules that now protect two Asian species, and how the sea otter recovered from fewer than 2,000 animals.
Table of Contents
When is World Otter Day 2027?
World Otter Day 2027 falls on Wednesday, May 26, 2027, the last Wednesday of May (IUCN Otter Specialist Group).
How the World Otter Day date is calculated
World Otter Day is held on the last Wednesday of May every year. To find the date for any year, follow these steps:
- Find the weekday of May 31 that year.
- If May 31 is a Wednesday, that is World Otter Day.
- If not, count back to the nearest earlier Wednesday.
Because May has 31 days, the last Wednesday always falls between May 25 and May 31. The table below lists the date for the next five years.
| Year | World Otter Day | Days before the end of May |
|---|---|---|
| 2027 | Wednesday, May 26, 2027 | 5 |
| 2028 | Wednesday, May 31, 2028 | 0 |
| 2029 | Wednesday, May 30, 2029 | 1 |
| 2030 | Wednesday, May 29, 2030 | 2 |
| 2031 | Wednesday, May 28, 2031 | 3 |
In 2028, World Otter Day falls on May 31, the latest possible date. The earliest possible date, May 25, next occurs in 2033.
What does World Otter Day commemorate?
World Otter Day raises awareness of the world’s otter species, nearly all of which are declining, and of the threats they face from habitat loss, pollution, and illegal trade. It does not mark a historical anniversary.
Who runs World Otter Day?
The International Otter Survival Fund runs World Otter Day. IOSF was established on Tuesday, November 16, 1993, after its founders watched otters in the Hebrides in Scotland, and it runs an otter hospital on the Isle of Skye (IOSF Impact Report 2023).
The table below gives IOSF’s key figures from its 2023 impact report.
| Measure | Figure |
|---|---|
| Founded | November 16, 1993 |
| First World Otter Day | 2016 |
| Countries holding World Otter Day events in 2023 | 40 |
| Otters cared for at the Skye hospital | 245 over 30 years |
| Countries where IOSF has supported projects | 98 |
| Supporters | About 160,000 in 39 countries |
| Children reached by education work in Tanzania | More than 20,000 |
The IUCN Species Survival Commission’s Otter Specialist Group, one of the oldest IUCN specialist groups, also promotes the day. It assesses otter species for the IUCN Red List (IUCN).
Otter species and their IUCN Red List status
The IUCN Otter Specialist Group works on 14 otter species, and only one of them, the North American river otter, is assessed as Least Concern (IUCN).
Many older sources give 13 species. The count depends on taxonomy, since some authorities treat the African and Congo clawless otters as one species, and the Otter Specialist Group’s own species pages profile 13.
The table below lists the species profiled by the Otter Specialist Group, with each one’s Red List category (IUCN Otter Specialist Group).
| Species | Scientific name | Range | IUCN Red List status |
|---|---|---|---|
| Sea otter | Enhydra lutris | North Pacific coasts | Endangered |
| Giant otter | Pteronura brasiliensis | South American rivers | Endangered |
| Marine otter | Lontra felina | Pacific coast of South America | Endangered |
| Southern river otter | Lontra provocax | Chile and Argentina | Endangered |
| Hairy-nosed otter | Lutra sumatrana | Southeast Asia | Endangered |
| Asian small-clawed otter | Aonyx cinereus | South and Southeast Asia | Vulnerable |
| Smooth-coated otter | Lutrogale perspicillata | South and Southeast Asia, Iraq | Vulnerable |
| Eurasian otter | Lutra lutra | Europe, Asia, North Africa | Near Threatened |
| African clawless otter | Aonyx capensis | Sub-Saharan Africa | Near Threatened |
| Congo clawless otter | Aonyx congicus | Central Africa | Near Threatened |
| Spotted-necked otter | Hydrictis maculicollis | Sub-Saharan Africa | Near Threatened |
| Neotropical otter | Lontra longicaudis | Central and South America | Near Threatened |
| North American river otter | Lontra canadensis | North America | Least Concern |
Five of the 13 profiled species are Endangered, and two more are Vulnerable. Red List categories are reassessed periodically, so check the IUCN Red List for the latest status before quoting a single species.
Sea otter or river otter: the difference
The sea otter differs from river otters in where it lives and how it keeps warm. The table below compares the two most searched species.
| Feature | Sea otter | North American river otter |
|---|---|---|
| Habitat | Coastal ocean, kelp forests | Rivers, lakes, wetlands |
| Insulation | Dense fur, no blubber | Fur, plus time spent on land |
| Fur density | 600,000 to 1,000,000 hairs per square inch | Lower |
| Conservation status | Endangered | Least Concern |
| Tool use | Uses rocks to crack shells | Not typical |
Sea otter figures come from the US National Park Service. The sea otter has no blubber layer, unlike other marine mammals, so its fur is its only insulation in cold water.
Why otters matter: the keystone species role
Sea otters are a keystone species: by eating sea urchins, they stop urchin populations from exploding and stripping kelp forests bare (US National Park Service). Without otters, urchins can turn kelp forests into “urchin barrens” with little other marine life.
River otters play a related role in freshwater systems. As predators at the top of wetland and river food chains, their presence generally points to clean water and enough fish to sustain them. This is why conservation groups often treat otter surveys as a measure of river health.
How the sea otter recovered
The sea otter shows how quickly an otter population can collapse and how protection can bring it back. The timeline below uses figures from the US National Park Service.
| Year | Event |
|---|---|
| 1741 | About 100,000 to 150,000 sea otters live in Alaskan waters when Russian fur traders arrive |
| 1900 | Hunting for fur reduces the world population to about 1,000 to 2,000 |
| 1911 | International protection begins |
| 1989 | The Exxon Valdez oil spill kills at least 1,000 sea otters |
| Today | About 168,000 off Alaska and Russia, and about 2,400 off central California |
The sea otter population today is roughly 100 times its 1900 low, but the species remains listed as Endangered because of its small, scattered populations and its exposure to oil spills.
Threats to otters
The main threats to otters are habitat loss, water pollution, hunting for fur, and the illegal pet trade. IOSF campaigns against the pet trade, the fur trade, and the use of snares (IOSF Impact Report 2023).
The illegal pet trade and CITES Appendix I
The pet trade is now one of the most serious threats to two Asian species. At the 18th Conference of the Parties to CITES (CoP18), held in Geneva in August 2019, governments moved the Asian small-clawed otter and the smooth-coated otter to CITES Appendix I (Malaysian Conservation). Appendix I bans international commercial trade in a species.
The proposal cited rising commercial exploitation in Southeast Asia and several cases of otters smuggled from Indonesia and Thailand to Japan, which it named as one of the largest markets for pet otters.
Owning an otter as a pet is not a conservation activity. Wild-caught otters taken for the trade are removed from already declining populations.
What World Otter Day is not
World Otter Day is a charity-led awareness day. It is not a UN international day, a public holiday, or a fixed-date observance. The table below sets it beside other wildlife and nature days in late May.
| Observance | 2027 date | Organiser | Fixed or moveable |
|---|---|---|---|
| World Otter Day | Wednesday, May 26 | International Otter Survival Fund | Moveable, last Wednesday of May |
| European Day of Parks | Monday, May 24 | EUROPARC Federation | Fixed, May 24 |
| International Day for Biological Diversity | Saturday, May 22 | United Nations | Fixed, May 22 |
| International Tea Day | Friday, May 21 | United Nations | Fixed, May 21 |
| World Environment Day | Saturday, June 5 | United Nations Environment Programme | Fixed, June 5 |
In 2027, World Otter Day falls two days after European Day of Parks 2027 and five days after International Tea Day 2027. World Environment Day 2027 follows 10 days later, on Saturday, June 5.
How World Otter Day is observed
World Otter Day is observed through events organized by IOSF, zoos, wildlife groups and schools, along with social media campaigns using #WorldOtterDay. The activities below appeared in IOSF’s 2023 report (IOSF Impact Report 2023):
- Educational workshops, including through IOSF’s Team Otter clubs for children
- Fundraising events for otter rescue and research
- Webinars on otter conservation
- Social media campaigns, which made #WorldOtterDay trend worldwide in 2023
To support otters beyond the day itself, IOSF and the Otter Specialist Group point to three practical actions: report otter sightings to local survey schemes, avoid buying from exotic pet sellers or “otter cafés”, and support groups that protect rivers and wetlands.
Frequently asked questions
When is World Otter Day 2027?
World Otter Day 2027 is on Wednesday, May 26, 2027. The International Otter Survival Fund holds it on the last Wednesday of May each year, so the date changes. In 2028, it falls on Wednesday, May 31, and in 2029, on Wednesday, May 30.
Who started World Otter Day?
The International Otter Survival Fund started World Otter Day in 2016. IOSF is a charity founded on November 16, 1993, with an otter hospital on the Isle of Skye in Scotland. By 2023, World Otter Day events took place in 40 countries on every continent except Antarctica.
How many otter species are there?
The IUCN Otter Specialist Group recognizes 14 otter species, though many sources give 13, depending on how the African clawless otters are classified. Only the North American river otter is assessed as Least Concern. Five species, including the sea otter and the giant otter, are listed as Endangered.
Why are Asian small-clawed otters endangered?
The Asian small-clawed otter is listed as Vulnerable, mainly because of habitat loss and the illegal pet trade. In August 2019, CITES moved it to Appendix I, which bans international commercial trade. The listing proposal cited smuggling from Indonesia and Thailand to Japan, one of the largest markets for pet otters.
Why are sea otters a keystone species?
Sea otters are a keystone species because they eat sea urchins, which would otherwise multiply and strip kelp forests bare. Where sea otters are present, kelp forests and the species that depend on them can survive. Where otters disappear, urchins can create “urchin barrens” with very little marine life.
How dense is sea otter fur?
Sea otter fur holds 600,000 to 1,000,000 hairs per square inch, according to the US National Park Service, the densest of any mammal. Sea otters have no blubber, so this fur is their only insulation in cold ocean water. That fur was also why hunters nearly wiped them out by 1900.
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