How is the humpback whale population growing in the Strait of Magellan?
- Published: 2012
- Authors: Juan Capella, Jorge Gibbons, Yerko Vilina, Lilián Flórez-González, Valeria Sabaj, Carlos Valladares
- Download the full study here
Study summary
This work compiles 13 years of intensive monitoring of humpback whales (Megaptera novaeangliae) in the Strait of Magellan, with the aim of estimating its abundance, population structure, birth rate and site loyaltyIt is one of the longest and most comprehensive studies conducted in the Southern Hemisphere outside of Antarctica.
Area of study: surroundings of Carlos III Island, Magallanes Region, Chile
Period: 1999 to 2011
Field effort: 969 days of observation, 533 days of navigation and more than 14,600 km traveled
Key findings
Abundance:
The estimated population in 2011 was 92 resident individuals (with confidence interval 86–98).
They were identified photographically 126 unique whales during the total period.
The estimated total population size is 132 whales.
Reproduction:
The crude birth rate averaged 9,4% annual.
The most frequent breeding rate was each 2 years (58%), followed by every 3 years (17%).
The estimated age for first birth was 5 to 6 years.
Structure and fidelity:
A was observed strong site loyalty: 82% average annual recapture.
Both males and females returned consistently each season.
Some whales were re-sighted during more than 9 consecutive years.
Stay in the area:
The whales remained on average 55 days per season (maximum: 156 days).
The 73% was seen between 2 and 20 days per season.
Risks to the population
The study warns that this reproductive and food aggregation is small, site-loyal and very vulnerable to human impacts such as:
Cargo and tanker traffic (existing and increasing)
Development of mining projects in nearby areas
Increased probability of fatal collisions with boats
Furthermore, the Chilean environmental assessment system has not sufficiently considered these impacts, according to the study.
Whalesound's commitment to science and conservation
Since its inception, Whalesound has been an active part of this study, providing logistics, observations, and scientific records. Each expedition we undertake contributes to the understanding and protection of Patagonian humpback whales.
