A unique opportunity to study fertility and maternal investment in the critically endangered kakapo (Strigops habroptilus)

Lead Research Organisation: University of Sheffield
Department Name: Animal and Plant Sciences


The kakapo (Strigops habroptilus) is a critically endangered flightless parrot native to New Zealand. Only 147 currently exist in the world, all managed on predator-free offshore islands by the New Zealand Department of Conservation's Kakapo Recovery Team. Managing the recovery of the population is challenging: kakapo only breed when conditions are good, and when they do, approximately 70% of their eggs fail to hatch. Of these unhatched eggs around 75% appear to be 'infertile' - that is, they show no sign of development. However, undeveloped eggs can result either from (i) fertilisation failure, potentially caused by insufficient or poor quality sperm, or (ii) early embryo death, which may be linked to poor female condition, inbreeding, or the environment. It is difficult to distinguish unfertilised eggs from those that have suffered early embryo death, but we have previously established methods for doing this, allowing us to identify and mitigate the underlying causes of hatching failure.

Kakapo breeding is highly unpredictable, being dependent on abundant food from several tree species with irregular fruiting cycles. Kakapo breeding seasons occur on average every 2-4 years and fewer than 50% of females typically lay eggs. There have been only three major breeding seasons - where the majority of females attempted to breed - in the last 20 years. This year (2019), exceptional ecological conditions have induced record-breaking reproductive rates, with over 90% of females laying eggs before the breeding season was even predicted to start. The Kakapo Recovery Team recently reported the first 5-egg clutch on record, and an unprecedented second round of nesting is expected later in the season. Until now, the kakapo's small population size and slow reproductive rate has limited our understanding of its reproductive biology, but this season's extremely unusual circumstances provide a once-in-a-generation opportunity to obtain the sample sizes required to address crucial questions about the causes of reproductive failure in this critically endangered bird.

Our proposed research will analyse all unhatched kakapo eggs produced this season, using our own established methods for determining whether hatching failure is due to fertilisation failure or early embryo mortality. We will quantify the number of sperm that reach ova to assess whether fertilisation failure is caused by a lack of sperm, and identify the developmental stage at which embryos die, with the aim of linking this to external causes. Finally, we will quantify how kakapo females differ in reproductive behaviour and investment by recording the number, size, and timing of eggs laid, and collecting data on how females care for their offspring. We will then assess how these traits are related to fertility, embryo survival, chick development, and other factors such as age, condition, and reproductive history, for which data are available from long-term monitoring by the Kakapo Recovery Team. This work will be crucial for planning the future management of this iconic species, and will substantially improve our broader understanding of reproductive problems in birds.

Planned Impact

Understanding and mitigating the causes of reproductive failure is a fundamental goal of conservation practitioners working with threatened species. We will provide the first ever assessment of true fertility rates and identify traits associated with infertility in the critically endangered kakapo, a species with over 70% hatching failure. We will reveal the extent to which early embryo mortality explains the kakapo's exceptionally high rate of hatching failure, and link infertility and embryo mortality to individual variation in maternal condition and reproductive investment. Working directly with the New Zealand Department of Conservation (DoC) Kakapo Recovery Team, we will provide conservation managers and practitioners with detailed, individual-specific information on kakapo reproductive behaviour and fertility. This information will be used to make key breeding management decisions that will reduce reproductive failure and improve hatching rates in this critically endangered bird.

In addition to its direct applications for conservation practitioners and policy makers, our proposed research will benefit those working in science education and the wider society through increased engagement with conservation issues. People care about the kakapo. Its plight is well-known, having been regularly featured on high-profile documentaries watched by millions, including Stephen Fry's 'Last Chance to See', David Attenborough's 'The Life of Birds', and more recently the BBC's 'New Zealand: Earth's Mythical Islands'. As a result, there is remarkable public interest in its ongoing conservation and breeding success, providing us with a broad audience to engage with our research. Our work will build on this existing interest, engaging the public in both New Zealand and the UK with conservation issues, reproductive biology, and behavioural ecology more generally. We will use the PI's exceptional experience in public engagement and outreach to develop an outstanding programme of activities for school audiences and the general public, as well as leveraging our considerable online and social media presence to disseminate our findings to a diverse and international audience. The appeal of the kakapo and applied conservation biology has real potential to inspire young people to pursue careers in science, providing a wider benefit for innovation and society.


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Description Kakapo have high levels of hatching failure and the majority of their eggs fail to develop at all. Undeveloped eggs have previously been assumed to be unfertilised, indicating a population-wide problem with male fertility. After a record-breaking kakapo breeding season in 2019, in which 252 eggs were laid, we were able to determine the fertility status of 125 of 129 undeveloped kakapo eggs. Contrary to previous assumptions, the majority of these eggs (n = 90, 72%) were in fact fertilised eggs that had died very early in development. The remaining 35 were unfertilised. Knowing that early embryo death is more common than fertilisation failure in kakapo will inform conservation management decisions by focusing future attempts to mitigate hatching failure on pair compatibility and females, rather than exclusively on males. Since both infertility and early embryo death occur within the population, our ability to identify which occurred for each egg will help the kakapo recovery team understand and separate the respective causes of the two problems.
Exploitation Route Our findings are currently being used by the New Zealand Department of Conservation Kakapo Recovery Team to inform conservation management decisions including selection of individuals for translocation and artificial insemination in future breeding seasons. This work is also likely to influence management decisions of other threatened bird species with similar hatching failure problems.

We have a paper currently in preparation with our Project Partners which we aim to submit in the next two months to disseminate our findings to the wider conservation community and general public.
Sectors Environment,Other

Description We have engaged the local community by consulting with representatives from Ngai Tahu (the local Maori iwi that NZ DOC works with on all operations in Southern South Island, NZ) on a bimonthly basis throughout the project. We have also specifically provided a non-academic report to Ngai Tahu on our findings, and garnered their support for our ongoing research.
First Year Of Impact 2020
Sector Environment,Other
Impact Types Cultural

Description Egg examination training for KRT conservation practitioners
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Influenced training of practitioners or researchers
Impact Training provided to KRT team member will improve the efficiency and outcomes of breeding decisions for kakapo in future breeding seasons, with direct benefits for the goals of the NZ Department of Conservation and for kakapo recovery.
Description Kakapo fertility information to KRT breeding managers
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Implementation circular/rapid advice/letter to e.g. Ministry of Health
Title Kakapo egg fertility and sperm numbers dataset 
Description Data on egg fertility for all undeveloped kakapo eggs from 2019 breeding season. Data on the number of sperm reaching eggs for all undeveloped kakapo eggs from 2019 breeding season. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Impact Currently being used to inform KRT on fertility issues within the kakapo population, which will influence conservation policy decisions regarding breeding and translocation of individuals. 
Description Kakapo Recovery Team, New Zealand Department of Conservation 
Organisation New Zealand Department of Conservation
Country New Zealand 
Sector Private 
PI Contribution We have worked directly with our project partner, the New Zealand Department of Conservation (DOC) Kakapo Recovery Team (KRT) to inform key decisions about breeding management of the entire kakapo species. We embedded the PDRA (Dr James Savage) within KRT for the majority of the project, thereby working directly with the conservation practitioners on a daily basis. The PDRA contributed to bimonthly meetings with policy makers and local stakeholders, providing a clear pathway for disseminating the conservation applications of our work.
Collaborator Contribution Key members of KRT have assisted our research, including Operations Manager Deidre Vercoe, Scientific Advisor Dr Andrew Digby, Technical Advisor Daryl Eason, and Senior Ranger Dr Jodie Crane, all of whom work directly with kakapo and other endangered New Zealand birds, and are members of the Kakapo Recovery steering group that makes key conservation management decisions. KRT have been heavily involved with implementing our project, and continue to be involved with our ongoing work. They hosted the PDRA for extended visits, contributed staff time for the collaboration, and maintain and trained the PDRA on their extensive 25 year kakapo breeding and behavioural database.
Impact We produced a dataset of fertility information for the entire kakapo population that has already been fed back to KRT to inform breeding management. We also have a publication currently in preparation based on this data.
Start Year 2019
Description Kakapo Research Consortium 
Organisation University of Canterbury NZ
Country New Zealand 
Sector Academic/University 
PI Contribution Involvement of NH in 2 consortium meetings (multi-university and NGO) to discuss direction of kakapo conservation genomics research, and inclusion as a partner on an external funding bid.
Collaborator Contribution Partners a leading a funding bid that NH is involved with to build up research from this award and providing intellectual input on related funding application currently being prepared by NH.
Impact No outcomes yet as funding applications still pending. Multi-disciplinary collaboration: genomics, conservation, reproductive behaviour.
Start Year 2020
Description BBC World Service CrowdScience interview 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Dr Nicola Hemmings featured in a BBC CrowdScience episode talking about fertility issues in wild animals, and as part of the interview that was included in the final cut, she talked about the kakapo fertility research that was done in this project.
Year(s) Of Engagement Activity 2021
URL https://www.bbc.co.uk/programmes/w3cszv6z
Description Guest Lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact First year undergraduates studying zoology attended at guest lecture by the PI which included this project as a case study on using research from evolutionary biology and behavioural ecology to inform conservation policy. The lecture sparked discussion among the audience and a number of students contacted the PI after the event to express interest in gaining more knowledge and experience in this field. The department has requested for the event to be repeated next year for the next set of incoming students.
Year(s) Of Engagement Activity 2020
Description Report to Ngai Tahu (local iwi in New Zealand) 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Other audiences
Results and Impact We wrote a report of our preliminary findings to be presented by KRT to representatives of Ngai Tahu (local iwi in New Zealand) to explain what we had found and the implications for kakapo, a culturally important species for Maori. This engagement work is important because it enhances the connection between our research and traditional Maori knowledge, and ensures cultural safeguarding of the samples we are working on. The report has also enabled us to garner support from Ngai Tahu for follow-on research.
Year(s) Of Engagement Activity 2019