The loudest hurrahs will be heard from animal welfare activists who are implacably opposed to government-sponsored culls to protect sensitive ecosystems from over-grazing by kangaroos, and loudly insistent that translocation or fertility control are equally effective alternatives that have the added advantage of being non-lethal.

The scientific evidence to back the efficacy of translocation and fertility control is not strong, however. And they are far costlier propositions than shooting. It is for that reason that Canberrans of a more realistic outlook will likely question its wisdom. Embarking on a trial that costs taxpayers $530,000 over two years and which is highly likely to deliver inconclusive results does not fit the description of good and sensible government at a time of fiscal restraint. The trial will, however, win the government some brownie points from animal rights activists – for what that is worth.

In this instance, cull protesters have Territory and Municipal Services Minister (and Greens MLA) Shane Rattenbury to thank for the CSIRO-administered trial. Last year, at the very time the government was announcing an increase of about 25 per cent in the numbers of eastern greys to be culled, Mr Rattenbury offered protestors a sop: the government would organise a fertility trial at the Gungaderra nature reserve in Gungahlin, with help and input from animal rights group Alphadog. Up to 500 animals would be tranquillised and then administered a gonadotropin-releasing hormone marketed under the brand name Ovuplant – and at a cost Alphadog director Marcus Fillinger claimed would be cheaper than shooting.

The trial, scheduled to begin in July, will be markedly different, and smaller, than the one outlined last May. About 200 animals from up to 10 sites with high female populations will be administered with one-shot doses of GonaCon, another gonadotropin-releasing hormone that has proved useful in controlling the fertility of wildlife and feral animals in the United States and which, according to Environment Minister Simon Corbell, has proven highly effective when individually injected into kangaroos. In a further departure from the Alphadog approach, the GonaCon for this trial will be delivered via dart.

Gonadotropin-releasing hormone is produced in the hypothalamus, and it signals the body to produce oestrogen, progesterone or testosterone. GonaCon works by "tying up" the GnRH produced within an animal's body so that it fails to trigger reproduction. It does this by inducing the body to make antibodies against its own GnRH. Immuno-contraception may be an elegant scientific solution to animal population control, but it is not universally lauded as such.

In 2006, when then TAMS minister John Hargreaves touted its potential in the Assembly, the late geneticist Professor Des Cooper warned that immune-contraception could make animals more vulnerable to infectious diseases. Anassessment of GonaCon by the US Department of Agriculture noted its negative effects on the immune system. The USDA also noted that the effectiveness on deer treated with a single injection of GonaCon, while impressive in the first year, dropped away markedly in the second year. The "need to capture and inject each animal" was a further limitation.

Administering GonaCon via dart would circumvent such issues, but bring with it a new set of problems, including botched delivery of the vaccine, trauma from poorly aimed darts and stress or injuries as a result of panicked flight. The biggest drawback of contraception, however, remains its cost, with some estimates that it will be triple that of culling.

Were the impracticalities and the cost of contraception to be considered in the cold light of day, it would likely be rejected out of hand as a viable and effective population control measure. But the public histrionics that culling elicits in the ACT (as distinct from the culling that routinely occurs in rural Australia) is considerable. During the 2014 cull, for instance, vehicles at a Parks and Conservation depot in Farrer were extensively damaged by vandals. So a desire by to assuage the opponents of culling is understandable. But in offering them up a fertility trial as a sop, the risk is that this will become a rod for the government's back.