Mandurah’s Freeze Branded Dolphins
You may have noticed that some of Mandurah’s dolphins have faint numbers on their fins. Many years ago when dolphins stranded here in Mandurah, freeze branding was the method used to help identify and keep track of the dolphins. Mandurah has been identified as a dolphin stranding hot spot, with the Peel-Harvey area being so shallow, the dolphins can get stuck in the shallows as they are navigating into these areas whilst looking for fish and get caught out by the tide. Many of our dolphins have stranded several times! We are lucky enough to have the Mandurah Dolphin Rescue Group in Mandurah, who have been rescuing our dolphins for over 20 years.
The first time dolphins were freeze branded in Mandurah was in October 1990. A group of ten dolphins were found in Lake Goegrup, near the Serpentine River swimming in a pool of deeper water but were unable to get out as the rest of the surrounded area was too shallow. They may have become trapped after chasing fish into the lake and then been caught out with the receding tide. Unfortunately two dolphins had already died, however the remaining eight dolphins were found in time to be rescued and then released into the Mandurah estuary. Wildlife officers from CALM, Department of Conservation and Land Management as it was known then were called out and with the help of volunteers they were able to capture the dolphins. Each dolphin was tagged, numbered, measured and given an overall check before being released. These were the first dolphins to be freeze branded with numbers Zero one to Eight. Since then many others have stranded in the shallows of the Peel-Harvey area.
Freeze branding involves immersing a brand in liquid nitrogen (dry ice) and then holding it against the dolphin’s skin. The skin cells where the brand touches are killed and the end result is a white mark that matches the shape of the branding iron. The marks should remain for over 20 years. By having these long lasting visible marks it helps to identify the animals and gain valuable information as to how long they survive and whether they strand again. This method is no longer used with the last dolphin, Twenty three being branded in 1997.
Some of the dolphins that were freeze branded can still be seen in the Peel-Harvey waterways today. Zero one and Fourteen are two adult males, often seen together. They have found themselves in trouble many times over the years with the most recent being at Herron Point in January 2018. This time they were trapped in a pool of deeper water but they were not able to get out due to low tides and surrounding sandbars. There was enough water and plenty of fish for them so a decision was made to monitor them over the next few days and in the end they were able to get out on their own with the higher tide. Read more about Zero One in Mandurah Dolphin Research project’s recent Fin Review.
We also often see Twenty two and Twenty one, mum and daughter. In March 1997 they were freeze branded then released into deeper water after stranding, along with Zero one and three other dolphins. At the time Twenty one was a young calf, she has had several calves of her own now with the latest Nikaila born in 2017. Early this year, Mum and calf found themselves trapped in the same place as Zero one and Fourteen! Luckily they managed to get out overnight with the high tide.
We would love to hear if you have seen any of these dolphins and any stories you may have about them. If you ever see a dolphin stranded or in distress please contact the Wildcare helpline on 08 9474 9055. Please feel free to ask any questions you may have below and we’ll have our expert dolphin team answer them. To book a dolphin tour with us, click here.