Srečanje znanstvenega odbora sporazuma ACCOBAMS

V Casablanci (Maroko) je med 11. in 13. januarjem 2010 potekalo 6. srečanje znanstvenega odbora sporazuma ACCOBAMS (Sporazum o ohranjanju kitov in delfinov Črnega morja, Sredozemskega morja in atlantskega območja ob njem ), ki se ga je na povabilo organizatorjev udeležil tudi Tilen Genov iz društva Morigenos. Znanstveni odbor je na srečanju preučil napredek (ali pomanjkanje napredka) na posameznih področjih varstva kitov in delfinov v Sredozemlju in Črnem morju. Zelo zaskrbljujoče je dejstvo, da navadni delfini (Delphinus delphis) še vedno izginjajo iz Sredozemlja, kljub poznavanju ključnih dejavnikov ogrožanja. Odbor je pripravil več priporočil za nadaljnje raziskovanje in varstvo kitov in delfinov na območju sporazuma, od držav podpisnic (med njimi je tudi Slovenija) pa je odvisno, ali bodo tudi ukrepale.

Whales saving seals

Survey to the Antarctic Peninsula lead scientists of NOAA Fishery Service to an interesting discovery, which was published in a popular article in the Natural History Magazine. The first author Robert L. Pitman has kindly allowed us to post this on Morigenos Blog.

The aim of the survey was to document remarkable hunting technique of the resident killer whales. The whales swim side by side to create a wave that washes the seal off an ice floe. Video of the hunt: http://www.orcaresearch.org/video_orca.htm.

After locating a pod of killer whales with satellite transmitters, the scientists noticed two humpback whales nearby. The whales seemed agitated by the killer whales’ presence, although they were not under attack. When researchers reviewed video footage, they noticed a seal between the humpbacks, which is what the killers were probably after. Later on, the pod tried to catch another seal, resting on the ice floe. In that moment, the same two humpback whales swam onto the scene, bellowing and thrashing around. The humpback whales were apparently harassing the killer whales and interrupted their action.

A week later the scientists spotted a different pod of killer whales, attempting to catch a seal resting on an ice floe. Two humpback whales were involved in the fight once again, but they were not the same two individuals as in the week before. When the killers washed the seal off the ice floe, it swam towards the humpbacks, seeking shelter. One of them turned belly-up, and placed the seal between its flippers. When killer whales moved closer it arched its chest out, which lifted the seal out of the water. When the seal started sliding towards the water, the whale pushed it back onto its chest with a flipper. Moments later the seal scrambled off and swam to the safety of a nearby ice floe.

Humpbacks have shown maternal instinct in this dangerous situation, although they did not have calves of their own. Allomaternal care has been seen recorded in several species. When a human protects an individual of another species, we call it compassion. If a whale does so, we call it instinct. But sometimes the distinction isn’t all that clear.

Source: R. Pitman and J. Durban. 2009. Save the seal! Nat. Hist. Mag. Nov. 2009.

Photo: Robert L. Pitman

Kiti rešujejo tjulnje

Odprava na Antarktični polotok je znanstvenike ribiške službe NOAA (National Oceanic and Atmospheric Administration Fishery Service) privedla do zanimivega spoznanja, ki so ga objavili v poljudni reviji Natural History. Prvi avtor Robert L. Pitman nam je prijazno dovolil, da zadevo objavimo tudi na Morigenos Blogu.

Cilj odprave je bil posneti izjemno tehniko lova tamkajšnjih ork. Z usklajenim plavanjem ustvarijo val, ki tjulnje odplakne s plavajočih ledenih ploskev. Video lova: http://www.orcaresearch.org/video_orca.htm.
Po lociranju skupine ork z oddajniki so v neposredni bližini ork opazili tudi dva kita grbavca. Iz njunega nemirnega vedenja so sprva sklepali, da sta razdražena zaradi njihove prisotnosti, čeprav ju orke niso napadale. Po pregledu video posnetkov dogodka so med grbavcema opazili tjuljnja, ki so ga po vsej verjetnosti orke nameravale upleniti. Kasneje je jata pričela z lovom na drugega tjuljnja, ki je počival na plavajoči ledeni ploskvi. V tistem trenutku sta na kraj dogajanja priplavala ista dva grbavca in pričela glasno pihati in udarjati po vodi s plavutmi. Grbavca sta, kot je kazalo, nadlegovala orke in znova prekrižala njihove načrte.

Teden kasneje so opazili drugo jato ork, ki je lovila tjulnja na ledeni ploskvi. V boj sta bila zopet vpletena dva grbavca, vendar ni šlo za iste živali kot teden poprej. Ko so orke uspešno odplaknile tjuljnja s plošče, si je ta zavetje poiskal pri grbavcih. Eden izmed grbavcev se je obrnil s trebuhom navzgor in tjulnja namestil med svoje prsne plavuti. Ob približevanju ork je kit izbočil prsni koš in s tem tjulnja dvignil iz vode. Ko je ta začel drseti nazaj proti vodi, ga je kit s plavutjo nežno potisnil nazaj na sredino (kliknite na fotografiji za povečavo). Nekaj trenutkov zatem se je tjulenj skobacal na bližnjo ledeno ploščo.

Grbavci so v nevarni situaciji morda pokazali materinski nagon, čeprav ni šlo za njihove mladiče. Alomaterinska skrb (ko neka žival skrbi za mladiča druge vrste) je bil opažen tudi pri drugih vrstah živalih. Ko človek obvaruje pripadnika druge vrste, to dejanje pripišemo usmiljenju. Če to stori kit, ga pripišemo nagonu. Včasih razlika ni preveč očitna.

Vir: R. L. Pitman and J. W. Durban. 2009. Save the seal! Nat. Hist. Mag. Nov. 2009.

Fotografija: Robert L. Pitman