By Dr. Valeria Vergara, Vancouver Aquarium Marine Science Centre research scientist
“The adults left the calf absolutely alone,” narrated Mathilde Michaud, our drone operator, onboard the research vessel the Bleuvet. When we reviewed the footage that evening this was crystal clear: a newborn beluga calf was left alone for nearly five minutes. It waited at the surface until the adults re-joined it and the group continued on its way down the river. This observation that beluga newborns can indeed be occasionally separated from the adults illuminates a fragment of a puzzle that needs urgent solving — why are beluga calves dying in the St. Lawrence Estuary? This endangered population has been losing its calves at unprecedented rates in the past decade, exacerbating a worrying decline. The answer is not simple, as a synergy of factors may be playing a role, including toxic algal blooms (the most likely culprit for the 2008 deaths), climate change, pollution, industrial developments and disturbance. Since no signs of disease were identified in any of the newborn carcasses examined, other factors that can contribute to separation from the mother are worth looking at.
As a research scientist with the Vancouver Aquarium, I spent three weeks in Tadoussac, Quebec, with our collaborator Robert Michaud (Director of the Group for Research and Education on Marine Mammals), studying whether underwater noise introduced by human activities interferes with the acoustic communication between beluga mothers and their newborn calves, and their ability to regain contact after separations. In their turbid underwater world, finding one another through vision would be as futile as it would be for us attempting to find one another in thick fog without using our voices. Belugas must rely on sound to do this, more specifically, on a system of mother-calf contact calls. If this system is compromised, at best, the energy demands on the animals can be taxed, and at worst, the pair may fail to reunite resulting in dire consequences for the calf.
But how often do beluga mothers and calves become separated? Do they always call when they are apart? Are those calls masked by noise? Eavesdropping on their underwater world with a hydrophone while simultaneously observing them from the air with a small, quiet drone to get a good view of their behaviour – including any separations and reunions – might provide us with some answers.
Good questions take patience and more than one field season to answer. Occasionally, all the factors align to produce an excellent piece of data. This was the case the day we managed to stay with the same herd for hours, from the relatively quiet Baie Sainte Margarite, where their calls could be heard loud and clear, to the deafening confluence of the Saguenay and the St Lawrence Rivers, where all we could hear was noise. As I noted ever-increasing noise levels on the computer screen, the drone was above our focal group — a few adults and juveniles and 2 newborn calves slowly but surely crossing the ferry lane in a tight formation. “They are slowing down, as if waiting to cross,” Mathilde described. Indeed, the footage later revealed one of the calves lagging ever so slightly behind, and the adult looking back at it with her flexible neck, and slowing down her body to accommodate her speed to her calf’s. In that kind of noise any separation would be risky. I can only imagine what it must be like for these acoustic creatures, tiny, naïve, new to the world, to traverse this literal wall of noise. It must be like having to crawl through a dark tunnel as a toddler.
Going over the material back at the Cetacean Research Lab really brings home what pairing these two technologies can allow us to learn. After decades of classifying beluga behaviours into general categories that reveal too little based on what one can observe at eye level (moving directionally, milling, surface active), the barrier is lifted and we are suddenly allowed into their world. The resulting level of detail is extraordinary, and what we learn, we hope, will get us closer to an answer that may tip the scale in favor of the survival of this endangered, iconic species.