Forefront of Avian Conservation-10. Ex situ conservation of Lagopus muta ─Progress in the past 5 years─

Ex situ conservation of Lagopus muta ─Progress in the past 5 years─

Toyama Municipal Family Park Zoo
Hitoshi Murai

This year marks the fifth year since the Rock Ptarmigan Protection and Breeding Project of the Ministry of the Environment of Japan started. The short-term five-year goal for ex-situ conservation in the Phase 1 Rock Ptarmigan Protection and Breeding Project Implementation Plan that was formulated by the Nagano Natural Environment Office of the Ministry of the Environment in 2014 mentioned the application of captive breeding technologies of the Svalbard ptarmigan, which is another subspecies whose numbers were accumulated in a zoo, in order to begin the captive breeding of the rock ptarmigan. Another task mentioned was the maintenance of a certain number of captive rock ptarmigans after giving due consideration to genetic diversity, and thereby establishing the captive breeding technology and implementation system that is needed for this. Furthermore, investigations on ideal captive breeding technologies that assume reintroduction to the wild were also planned.

Start of rock ptarmigan breeding
In 2015, fertilized eggs that were collected from the Mount Norikura population, whose habitat was stable and whose population dynamics were understood by researchers, were accepted by zoos, whereupon artificial incubation and brooding initiatives were started, using the experience obtained with the Svalbard ptarmigan as a reference (Fig. 1). Toyama Municipal Family Park Zoo (henceforth, “Toyama”) received five eggs in the latter stages of development, and Ueno Zoo (henceforth, “Ueno”) received five eggs prior to brooding. As a result, four chicks were hatched in Toyama, but one of these died six days after hatching. The remaining one egg had stopped growing in the early stages of development. In Ueno, chicks hatched from all five eggs, but all of them died around two months after hatching.

Fig. 1. Rock ptarmigan chicks that first hatched in Toyama from eggs that were collected in Mt. Norikura

The three birds that hatched in Toyama grew well, but they were all male. Therefore, Toyama could not engage in captive breeding efforts, and in 2016, fertilized eggs from the Mount Norikura population were given to Omachi Alpine Museum (henceforth, “Omachi”) in Nagano Prefecture in addition to Toyama and Ueno, and the three organizations engaged in the hatching and brooding of the chicks. Toyama, Ueno, and Omachi each received four eggs and engaged in artificial incubation, the result of which was the hatching of all the eggs in the three zoos and their subsequent growth. There was one female chick that hatched in each zoo, therefore, in 2017, the first captive breeding efforts were initiated as part of the protection and breeding project.

Start of captive breeding
In 2017, captive breeding began in Toyama, Ueno, and Omachi following the formation of a pair in each zoo. In the first year, all zoos applied their breeding experience with Svalbard ptarmigans to allow the pairs to live together and mate in dedicated cages, constantly replacing the laid eggs with fake eggs, and hatching them using an incubator. When the breeding was successful, the zoos aimed to form pairs with no blood relation in the next breeding year and to increase the number of captive zoos by sending some of the fertilized eggs that were laid in each zoo to the other zoos, as well as transferring them to Ishikawa Zoo (henceforth, “Ishikawa”) and Nasu Animal Kingdom (henceforth, “Nasu”), which kept Svalbard ptarmigans in captivity, in order to hatch and brood them there.

The total number of eggs laid by the three pairs was 60 (Toyama: 20, Ueno: 22, and Omachi: 18), which was approximately three times the average number of eggs laid by rock ptarmigans in the wild (6–7 eggs).

The results of artificially incubating 58 out of the 60 laid eggs after excluding broken and soft eggs showed that 48 eggs were fertilized (Toyama: 16, Ueno: 16, Omachi: 16). The fertilized egg rate of the hatched eggs was 83%, which was a higher percentage than the 25% observed among the Svalbard ptarmigans. Furthermore, 22 fertilized eggs among these 48 were transferred, and hatching and brooding efforts were continued at five zoos.

As a result, a total of 22 individuals were successfully hatched (Toyama: 5, Ueno: 6, Omachi: 6, Ishikawa: 1, and Nasu: 4). The hatching rate for the fertilized eggs was 46%, which was slightly lower than the hatching rate of 56% observed among the Svalbard ptarmigans.

Of the hatched individuals, 10 died within two weeks of hatching, and the remaining 12 continued to grow. The survival rate six months after hatching was 55%, which was higher than the survival rate of 49% recorded among the Svalbard ptarmigans.

The captive breeding during this first year of the project resulted in successful breeding, but new issues have become evident such as controlling the excessive laying of eggs, improving hatching rates, and improving chick growth rates.

Aiming to establish captive breeding techniques
In 2018, prior to breeding, one male individual in Omachi was transferred to Nasu in order to allow for the latter to undertake breeding, which had only one female individual. This was the first attempt with rock ptarmigans, but with the past experience using Svalbard ptarmigans, the zoos were able to successfully transfer the individual.

In 2018, the four zoos of Toyama, Ueno, Omachi, and Nasu engaged in breeding efforts with the aim of improving captive breeding techniques by resolving the issues that became clear in 2017. As a solution to the issue, they investigated making the female calm and ready for breeding, forming a pair in a large room without using a dedicated cage, and keeping a distance from the female when a person enters the room during breeding period. Furthermore, they left the laid eggs as is and exchanged them with fake eggs after approximately two weeks had elapsed, thereby reducing the number of times that the people approached the nest.

As a result, the three females in Toyama, Ueno, and Nasu laid a total of 31 eggs (Toyama: 11, Ueno: 13, and Nasu: 7), approaching the number of eggs laid in the wild. For some reason, the female in Omachi did not lay any eggs.

Of the 31 eggs laid, 26 were artificially incubated, 17 of which were fertilized. The fertilized egg rate of the eggs that underwent artificial incubation was 65%, which was lower than the rate of 83% in 2017.
Additionally, of the 17 fertilized eggs, 12 chicks hatched. The hatching rate of the fertilized eggs was 71%, which was higher than the rate of 46% in 2017. Of the 12 hatched chicks, seven grew up, with three dying within one week of hatching and two dying 2–3 months after hatching. The survival rate of the chicks six months after hatching was 58%, which was slightly higher than the rate of 55% in 2017.

Additionally, the two females in Toyama and Ueno, which engaged in breeding efforts, exhibited incubation behavior and were allowed to continue incubation, but the eggs did not hatch because they either stopped growing in the early stages of development or were unfertilized.

New challenges
In 2015 and 2016, efforts were made for hatching and brooding via artificial incubation of fertilized eggs, and in 2017 and 2018, efforts were made for breeding via artificial incubation, and there was a sense of improved breeding techniques each year.

Meanwhile, it was considered that a breeding technique that was closer to wild conditions was necessary when assuming that the individuals will be reintroduced to the wild according to their habitat conditions in the future. In 2019, five years into the project, Toyama has engaged in breeding methods using the incubation of chicks by the mother bird (Fig. 2). As a result, the mother began incubation immediately after laying 10 eggs in the nest. The mother bird brooded for over 23 hours a day, and on July 3–4, which was the 22nd or 23rd day after brooding, eight chicks hatched. However, as the chick began to leave the nest and move around, the mother bird was observed to occasionally chase after the running chicks or peck at their heads, and on July 6, three chicks died due to being pecked on their heads by the mother bird. This was an abnormal behavior that would be unthinkable among wild rock ptarmigans. If left to the mother bird to brood the chicks as is, then more chicks would have died, so the remaining five chicks were separated from the mother bird and switched to artificial brooding. The five chicks are currently growing well.

Fig. 2. Rock ptarmigan chicks that were hatched following incubation by mother bird

This incident raised a new issue of brooding by the mother bird. All captive populations, including this mother bird, were rock ptarmigans that had undergone artificial brooding. Analyses of the incident will be conducted starting from now and improvements considering future breeding will be undertaken to determine whether this was an instance of an abnormal behavior or whether improving the current environment would eliminate the abnormal behavior.

Looking back on five years of efforts
The captivity of the rock ptarmigan began from 2015, and the breeding by artificial incubation that was started from 2017 increased the overall number of captive individuals in the zoo. Furthermore, the transfer of fertilized eggs and adult birds enabled the formation of pairs for breeding that took into account the maintenance of genetic diversity, and the number of zoos that participated in the breeding activities also increased. Additionally, the number of eggs laid was close to that in the wild, and the hatching rate and survival rate of chicks six months after hatching were improved.

Meanwhile, issues such as improving the fertilized egg rate, decreasing the mortality rate of chicks in artificial brooding, and the brooding behavior of the mother bird remain unresolved. There is a need to appropriately analyze each individual breeding case, set the goal of establishing captive breeding techniques in the future, and engage in captive breeding.

Furthermore, during the past five years, the Basic Agreement on the Promotion of Biodiversity Conservation (2014) that was concluded between the Japanese Association of Zoos and Aquariums (JAZA) and the Natural Environment Bureau of the Ministry of the Environment was used as a foundation for strengthening cooperation between the Ministry of the Environment and JAZA, and each zoo has cooperated with and has been working on ex-situ conservation with its respective roles and goals under the leadership of the JAZA Biodiversity Committee. Furthermore, joint research with university researchers has been advanced while receiving advice from researchers on the birds’ habitats, with the aim of establishing captive breeding techniques. We realize that these collaborations will continue to be important in the future when working on ex-situ conservation of not only the rock ptarmigan but of other species as well.