ORLANDO, Fla. — When a SeaWorld Orlando killer whale succumbed to a sudden illness Monday evening, it was the third killer-whale death at a SeaWorld marine park in just four months and the 13th in the past 14 years, according to federal records.

The death of Kalina, a 25-year-old female, followed that of Taima, a 20-year-old female who died giving birth to a stillborn calf at SeaWorld Orlando in June, and Sumar, a 12-year-old male who died last month at SeaWorld San Diego.

SeaWorld said it will conduct a necropsy to determine an exact cause of Kalina’s death, a process that will take as long as six weeks. The company has not yet released the results of the necropsies it performed on Taima and Sumar, though it has said Taima’s death was directly related to the birthing process.

“”We are deeply saddened by the loss of any animal. They are part of our family,”” SeaWorld spokeswoman Becca Bides said Tuesday morning. “”We take the loss of any of our animals extremely seriously and we are certain that these deaths are not related.””

The trio of deaths comes amid what may be the most challenging period in Orlando-based SeaWorld Parks & Entertainment’s nearly 50-year corporate history. SeaWorld has faced intense criticism since the Feb. 24 death of SeaWorld Orlando trainer Dawn Brancheau, who was battered and drowned by one of the company’s killer whales.

Brancheau’s death prompted the U.S. Occupational Safety and Health Administration to fine SeaWorld $75,000 and recommend that trainers never again be allowed unprotected contact with the orca that killed Brancheau, though SeaWorld is contesting the findings. The tragedy also fueled criticism from animal rights activists, who argued that the attack was the result of stress endured by killer whales in captivity.

The recent orca deaths have provided more ammunition for critics. Killer whales in the wild typically live much longer than Kalina, Taima or Sumar; females have a life expectancy of about 50 years and can reach 80 or 90 years of age, according to the National Marine Fisheries Service, while males live for about 30 years and can reach 50 or 60 years old.

According to Fisheries Service records, 13 killer whales have died at SeaWorld’s marine parks in Orlando, San Diego and San Antonio since 1996. The animals ranged in age from less than 1 year old to approximately 23 years old. The causes of death have included multiple cases of pneumonia, encephalitis and gastrointestinal ailments, according to the records.

Naomi Rose, a senior scientist at the Humane Society of the United States and a longtime critic of SeaWorld, said the deaths of Kalina, Taima and Sumar — all of whom were born in captivity — suggest that captive-born animals fare no better than wild-caught ones.

“”There’s something about the whole confinement and space and lack of family … that the stress is just pervasive,”” Rose said. “”It may be at a low level, but it’s persistent and low-level stress can be very dangerous over the long term. And they’re not living very long.””

SeaWorld, which was sold last fall by beer giant Anheuser-Busch InBev to the Blackstone Group, currently has 23 killer whales in its corporate collection, including four it has loaned to Loro Parque in the Canary Islands and one it has loaned to Niagara Falls, Ontario, and one it has on loan from the Barcelona Zoo. Six orcas are at SeaWorld Orlando.