Comparing progesterone in blubber and serum to assess pregnancy in wild beluga whales (Delphinapterus leucas)

Caroline E C Goertz; Kathy Burek-Huntington; Katie Royer; Lori Quakenbush; Tonya Clauss; Roderick Hobbs; Nicholas M Kellar

doi:10.1093/conphys/coz071

Comparing progesterone in blubber and serum to assess pregnancy in wild beluga whales (Delphinapterus leucas)

Conserv Physiol. 2019 Nov 11;7(1):coz071. doi: 10.1093/conphys/coz071. eCollection 2019.

Authors

Caroline E C Goertz¹, Kathy Burek-Huntington², Katie Royer², Lori Quakenbush³, Tonya Clauss⁴, Roderick Hobbs⁵, Nicholas M Kellar⁶

Affiliations

¹ Alaska Sea Life Center, 301 Railway, Seward, AK 99664, USA.
² Alaska Veterinary Pathology Service, 23834 The Clearing Dr, Eagle River, AK 99577, USA.
³ Alaska Department of Fish and Game, Fairbanks, AK 99701, USA.
⁴ Georgia Aquarium, Atlanta, GA 30313, USA.
⁵ Marine Mammal Laboratory, National Marine Fisheries Service, Nationa Oceanic and Atmospheric Administration, Seattle, WA 98115; 6130 NE 204th St., Kenmore, WA 98028, USA.
⁶ Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, LaJolla, CA 92037 USA.

Abstract

The Cook Inlet population of beluga whales (Delphinapterus leucas) is listed as endangered and continues to decline for largely unknown reasons; however, there is some evidence that poor reproductive success is a contributing factor. Pregnancy is difficult to detect through observation, and, there is reluctance to capture endangered beluga whales for reproductive tract imaging via ultrasound or to obtain suitable samples for pregnancy assessments. An endocrine analysis of blubber biopsies collected by remote darting could represent a minimally invasive way to identify pregnant females and compare pregnancy rates among years or populations. Studies have validated the use of blubber biopsies to identify pregnant females in other cetacean species, but not beluga whales; therefore, validation of blubber progesterone levels to proven tests that reliably detect pregnancy was needed for this species. As part of a larger study, we sampled blood and blubber from live-captured beluga whales (21 females, 26 males) in Bristol Bay, Alaska. Progesterone levels were determined in serum samples obtained from all animals and in blubber samples from a subset (14 females, 13 males) to determine pregnancy status, estimate the stage of pregnancy, and evaluate the suitability of using blubber alone for these assessments. In general, there was distinct separation of high levels of progesterone in serum and blubber for presumed pregnant females and low levels for males and presumed non-pregnant females. Blubber progesterone levels in two females (14% of females tested) were intermediate (i.e. ambiguous); their corresponding serum levels were consistent with being pregnant in one case and not being pregnant in the other. Except for these two intermediate values, pregnancy status of beluga whales could be determined from blubber alone, thereby providing a valuable tool to better understand reproduction dynamics from populations that cannot be captured for examination.