Kiwi conservation conundrum
How blinkered evolutionary thinking might be hampering kiwi conservation efforts (and conservation in general).
Published: 19 August 2021 (GMT+10)
Although they have no official status as a national emblem, the kiwi is a treasured icon of New Zealand culture and is widely believed to be our national bird. Go anywhere in the world and tell someone you’re from New Zealand and, more often than not, you’ll be called a ‘Kiwi’. Given the iconic status of these birds, it is not surprising that kiwi are considered to be the flagship for conservation in this country and are often used as a measure of the success, or otherwise, of conservation efforts.
An icon in decline
There are currently five recognised species of kiwi, with various assigned conservation threat-levels according to the New Zealand Threat Classification System (figure 1): brown kiwi (at risk: declining), great spotted kiwi/roroa (threatened: nationally vulnerable), little spotted kiwi (at risk: recovering), rowi (threatened: nationally vulnerable), and tokoeka (threatened: nationally critical).1
While populations in managed, predator-free facilities are growing, overall numbers are declining at an alarming rate and kiwi “may disappear from the mainland in our lifetime”.2
In 2013 researchers at Victoria University revealed a major concern for the conservation of one species in particular. All little spotted kiwi (LSK) were found to be descended from just five birds moved to a sanctuary in 1912 when fears of extinction were first raised.3 As such, LSK have extremely low genetic diversity, putting them at heightened risk of extinction should disease strike. This is of particular concern, as LSK are the one species that are classified as ‘recovering’.
On reading of this research, I was reminded of a boat trip that my wife and I took some years ago in the Marlborough Sounds, at the top of New Zealand’s South Island.
Our tour guide was telling us about conservation efforts in the area and, as we passed one particular island, she related an anecdote about a potentially ‘embarrassing’ situation for the Department of Conservation (DOC). Apparently, two species of kiwi under DOC care, LSK and rowi, had managed to interbreed. Although we were not told why this was embarrassing, I assumed at the time it was either because DOC workers hadn’t expected hybridization to be possible, or because they had allowed two species in their care to get too close together. When they realized what had happened, DOC relocated the hybrid birds to this island, to isolate them from the other kiwi and prevent further interbreeding (and, it was wryly suggested, in the hope that the ‘problem’ would go away). To add to the embarrassment, the hybrid population was, apparently, thriving.
Prompted by news of the perilous state of LSK conservation, I contacted DOC to check the veracity of this story. An email from a DOC Biodiversity Ranger confirmed that it was, in fact, true. The hybrid birds were discovered in the Okarito kiwi sanctuary, on the West Coast of the South Island, and placed on Allports Island to prevent further hybridization into the rowi population.
Lending tacit support to the implied problem this hybridization presented, Allports is not a DOC managed island and, as such, is highly unlikely to be predator-free. And, according to the email, the hybrid kiwi were known to have produced young, but they “haven’t been assessed for some time”.
This is not the only example of hybridization of kiwi and controversy over the value of the offspring to conservation. There is also a population of brown kiwi on Ponui Island, off the coast of the North Island, that are identified as hybrids due to interbreeding of individuals translated from genetically distinct populations of the same species.4 Again, the Ponui Island hybrid kiwi are “highly successful in their island habitat”, even in the presence of predators such as feral cats. Yet, despite this seeming success, these birds have been described as having “no genetic value whatsoever for use in restoration”.
Species and hybridization
The definition of what comprises a species today is actually very vague. A biological definition of a species (Mayr) is all those organisms able to interbreed and produce fertile offspring. However, the concept of reproductive isolation allows for separate species in cases where there are barriers to reproduction. These barriers are often genetic, but can also be environmental. For example, land and marine iguana of the Galapagos Islands are classified as separate species due to adaptations that allow them to live in very different environments, but interbreeding is possible, and hybrids have been observed (Hybridization shaking up the evolutionary Tree of Life—what does it mean for creationists?).
In the wild, LSK and rowi are geographically separated. Their hybridization—unexpected as it might have been—seems unlikely to affect their classification as separate species.
Benefits of hybridization to genetic health
We know that small, genetically isolated populations often exhibit increased incidence of genetic disorders over time. The breeding of dogs is a very good example (even though this involves human intervention and dogs are considered to be one species). Dogs bred for specific characteristics often develop related, and seemingly unrelated, hereditary problems (e.g. Pugs have breathing problems due to their flat faces, Cavalier King Charles spaniels (all descended from six dogs) are prone to mitral valve disease and heart failure5).
We also know that cross-breeding of dogs results in reduced incidence of genetic disorders and that ‘mongrels’ are usually much healthier than their pedigree parents. This ‘hybridization’ is actually encouraged by animal specialists and is (grudgingly?) accepted by breeders of pure-bred dogs provided the pedigree gene pool is not diluted.
Given the current conservation status of kiwi, with numbers reducing by as much as 2% per year and fewer than 70,000 birds left (from a population of several million 100 years ago)6, it seems pertinent to ask why the success of hybrid kiwi populations is deemed to be of limited value to conservation. Could it be that blinkered evolutionary dogmatism is hindering efforts to save the kiwi, and might this also be the case with other endangered species?
Different starting points lead to different priorities
Conservation efforts, in general, seem to focus almost exclusively on saving individual ‘species’.7 This is presumably based, to large extent, on the assumption that these species have accumulated unique genetic traits as a result of evolution over millions of years. The five kiwi species, for instance, are believed to have evolved from a common ancestor that existed approximately 50 million years ago8. If this were true, then it’s not surprising that hybridization, and particularly hybridization due to human intervention, is frowned upon. It would effectively be undoing millions of years of evolutionary ‘progress’ and, if you take this thinking to its logical conclusion, might even prevent the future arrival of some completely new kind of organism!
But this focus on preserving unique genetic traits at the expense of overall genetic health, as in the case of LSK, heightens the risk of extinction and the resultant loss of overall genetic variety.
From a Creationist perspective, however, we know that the different populations have appeared over a much shorter timeframe (<4,500 years)—again, from a common ancestor—due to genetic drift and loss of genetic information. In this scenario, hybridization is likely to be a positive for conservation in many circumstances, as it would reintroduce genetic diversity to the wider population that might otherwise have been lost. Yes, individual ‘species’ might be lost, but extinction of the kind would be much less likely (or at least significantly delayed).
Damned if we do, damned if we don’t
On the one hand, human activity—and destruction of habitat, in particular—is held up as a major contributing factor in the accelerating loss of biodiversity world-wide.9 But, on the other, our attempts to right the wrongs of our impact on the environment are seemingly hamstrung based on a flawed interpretation of where this biodiversity came from in the first place.
Am I suggesting wholesale hybridization of closely related species across all created kinds? Not at all! Individual species are a testament to the ingenuity and foresight of the Creator, who built genetic variety into each kind so that populations could adapt to different environments in a post-Fall (and post-Flood) world. And they are a big part of the awe-inspiring beauty of Creation.
But if a species is on the verge of extinction, surely it makes sense to do everything in our power—including intervention to achieve natural outcomes that might otherwise not happen—to preserve genetic variety before it is lost forever.
References and notes
- Department of Conservation, Facts and threats to kiwi, doc.govt.nz/nature/native-animals/birds/birds-a-z/kiwi/facts/, accessed 8 July 2021. Return to text.
- kiwisforkiwi.org/about-kiwi/kiwi-facts-characteristics/, accessed 8 July 2021. Return to text.
- O’Callaghan, J., Genetic weakness threatens rare kiwi, stuff.co.nz/dominion-post/8674214/Genetic-weakness-threatens-rare-kiwi, 15 May 2013. Return to text.
- As reported in Undin, M., Lockhart, P.J., Hills, S.F.K., Castro, I., Genetic Rescue and the Plight of the Ponui Hybrids, Front. Conserv. Sci. frontiersin.org/articles/10.3389/fcosc.2020.622191/full, 15 January 2021. Return to text.
- Dog Breed Health, A Guide to Genetic Health of Dogs, dogbreedhealth.com/list-of-dog-breeds/, accessed 8 July 2021. Return to text.
- Kiwis for Kiwi, kiwisforkiwi.org/about-kiwi/kiwi-facts-characteristics/, accessed 8 July 2021. Return to text.
- Fenster, C.B. et al., Conservation and genetics, Yale J. Biol. Med. 91(4):491–501, 2018. Return to text.
- Kiwis for Kiwi, kiwisforkiwi.org/about-kiwi/kiwi-facts-characteristics/how-kiwi-evolved/ Return to text.
- Wildlife conservation, worldwildlife.org/initiatives/wildlife-conservation, accessed 14 July 2021. Return to text.