Humpbacks arrive December, peak January–February, depart March. Central American–Mexican Pacific population; feeds summers off British Columbia and Gulf of Alaska. Calves common Jan–Feb. 838 GBIF records 2000–2025 in this corridor. Dolphins (bottlenose, common, pantropical spotted) are year-round residents; GBIF records are sparse (8–34 per species) reflecting low survey effort, not low abundance.
When to look
What you're likely to see
- Megaptera novaeangliaeCommon · Dec–Mar
- Stenella attenuataCommon · seasonal (offshore)
Frequency from 25-year GBIF records. Humpback dominates (838 of 889 total records). Dolphin counts reflect sparse observation coverage — actual encounter rates nearshore are higher than records suggest.
Sparse coverage for dolphins
Bottlenose (9 records), Common (8 records), and Bryde's (0 records) are severely underrepresented in GBIF for this corridor. Year-round presence is documented in the regional literature. The absence from the database reflects survey effort, not species absence. Any Bryde's whale sighting here would be exceptional — document and report to iNaturalist.
Five species documented in this corridor
Humpback whale
Megaptera novaeangliae LC ↑ Common · Dec–Mar Last reported: —The signature cetacean of the Guerrero winter. Humpbacks arrive from North Pacific feeding grounds to breed and calve in these warm, shallow waters. Adults reach 14–17 m; calves born January–February are frequently sighted alongside mothers. 838 GBIF records 2000–2025 in this corridor.
Bottlenose dolphin
Tursiops truncatus LC → Uncommon in records — common in practice Last reported: —The most commonly encountered dolphin nearshore. Work the surf line and offshore channels year-round, often in groups of 5–20 animals. Curious — they will sometimes bow-ride fishing boats. Adults reach 2–4 metres.
Common dolphin
Delphinus delphis LC → Uncommon in records — sparse coverage Last reported: —Among the most numerous cetaceans globally. Typically seen offshore in large groups. Adults 1.7–2.4 m with striking yellow-and-grey flank pattern.
Pantropical spotted dolphin
Stenella attenuata LC → Common · offshore (effort-normalized Sep–Nov) Last reported: —One of the most abundant dolphins in the eastern tropical Pacific. Fast, acrobatic, found offshore in large schools. Adults 1.6–2.5 m. 34 GBIF records 2000–2025 in this corridor.
Bryde's whale
Balaenoptera edeni LC → No records in study area Last reported: unconfirmedA medium-sized baleen whale (12–15 m), one of the few rorquals that remains year-round in tropical waters. Documented in eastern tropical Pacific, but rare in this specific corridor (0 GBIF records 2000–2025).
Zero GBIF records for this corridor. Possible but unconfirmed.
Recent sightings
GBIF records within 150 km, updated in real time. Most originate from iNaturalist and research surveys.
Sources
- GBIF Occurrence Search API, bbox lat 16.2–19.0°N / lon -102.9–-99.9°W, 2000–2025, hasCoordinate=true.
- Humpback Dec–Mar window: peer-reviewed literature for Mexican Pacific breeding ground; confirmed by GBIF counts.
- Dolphin records sparse (n=8–34) — reflects low survey effort, not low abundance.
- Bryde's whale: 0 GBIF records; present in eastern tropical Pacific.
- IUCN: all 5 species Least Concern. Humpback downlisted from Vulnerable in 2008.
Data last refreshed: —