A baby Māui dolphin - thought to be a few days old - has been found dead on Karioitahi Beach, west of Pukekohe, on Wednesday.
DOC's marine technical advisor Kristina Hillock said the animal's gender and exact age were unknown.
"The discovery of the animal was reported to DOC and our local team and iwi representatives responded as soon as practical to retrieve it."
It has been sent for necropsy at Massey University, the results of which are expected in around six week.
"We're keen to understand more about this animal, but we need some robust science undertaken."
Hillock said DOC was keen to remind the public to report any dead Māui or Hector's dolphins as soon as possible, as this provided the best opportunity for necropsy and science to be carried out to learn more about the dolphins.
Sightings of live dolphins anywhere in the country could also be reported to DOC's hotline 0800 362 468.
DOC also has an online reporting form on its website, including a portal to upload pictures or video.