( CNN ) -- The unexplained beachings of scores of dolphins over the past month along Cape Cod , Massachusetts , is the largest `` single-species event '' of its kind on record in the northeastern United States , a marine mammal specialist said Monday . A total of 129 common dolphins have been found since the animals began stranding themselves in early January , said Katie Moore , marine mammal rescue and research manager for the International Fund for Animal Welfare . Team members have been able to successfully release 37 of the 54 they were able to recover alive , but 75 others were dead or had to be euthanized on the spot , for a total of 92 dead , Moore told reporters in a conference call . Specially equipped trailers have been used to treat and transport the living dolphins . The ones that are healthy enough are taken to the outer Cape Cod coast to be released . Nine of the dolphins have been tagged with satellite tracking devices , Moore said , and most of the six that are still transmitting are north of Cape Cod , `` where dolphins should be . '' While dolphin strandings are not uncommon on the cape , Moore said this event is extraordinary in its `` protracted '' nature as well as the number of dolphins involved . `` We 've seen see an ( annual ) average of 228 strandings of dolphins and seals over the past 12 years '' in the International Fund 's Northeast region , which spans from Virginia to Maine , Moore said . `` There is a large variability year to year , '' she said , but this event represents `` more than half my annual average in a month . '' Moore said the International Fund staffs a 24-hour hotline , and when they get reports `` from beach-goers or anyone who finds an animal , '' they alert one of their 300 trained volunteers and dispatch them to the scene . These responders are able to relay information about the dolphin 's species , sex and condition . Once beached , a dolphin is vulnerable to predators and susceptible to organ damage and sunburn . If a dolphin is still alive , the responders get it onto its stomach , if it is not already , for easier breathing , keep away seagulls that would otherwise peck at it , and warm it with blankets or cool it with water as necessary , Moore said . Necropsies have been performed on nine of the dolphins , and blood and microbial swab samples have been taken from some that were found alive , Moore said , but so far no pattern of disease or trauma has been found that would point to a cause . Although the winter and early spring are the normal time of year for dolphin strandings to occur , the weather this season has been unusually warm , leading to speculation about climate change and subsequent `` distribution of prey '' as a possible causes . Last week , Wellfleet harbormaster Michael Flanagan explained that usually , in the winter , `` the harbor ices over and inhibits the animals from coming close to the shore . But now that the water is warmer , we 're seeing lots more dolphins washing up than ever before . '' However , the International Fund 's Moore cautioned , while climate or other external factors such as acoustic disorientation ca n't be ruled out , `` we do n't have a single answer . '' `` As time goes on we can put more of the pieces of the puzzle together , '' she said . `` The sad fact in these events is that we often never come up with that answer , and that is incredibly frustrating . '' She did , however cite the nature of the dolphins and the geology of Cape Cod as two contributing factors in these events , historically : . `` Common dolphins are incredibly social animals and form bonds to forage for food and avoid predators , '' she explained . Those bonds , while they serve the animals greatly in the open ocean they 're accustomed to , can be devastating when the creatures are brought in contact with Cape Cod 's gently sloping shallows and convoluted estuaries , which are `` very foreign to these species . '' Moore said the event , because of its scale and duration , is taking `` a huge toll '' on the resources of the animal rescue and advocacy group , financially and physically . `` This is very hard labor . These animals can weigh 200 or 300 pounds each , '' she said . The organization , which gets its funding through donations and grants , has a base operating budget of less than $ 300,000 , and she estimated this event has coast `` at least 50 or 60 thousand dollars , '' not including staff time . CNN 's Cameron Tankersley and Kendall Green contributed to this report .
`` It 's the largest single-species event '' in the Northeast , a marine mammal expert says . Comment: Necropsies have been done on nine animals ; no cause has been determined . Some of the released animals have been tracked north of Cape Cod , where they belong .