Substitute for cow's milk?
OPINION: Scientists claim to have found a new way to make a substitute for cow's milk that could have a radical effect on the dairy industry.
This is an important finding in research for a master's thesis on wildlife management by a Southland Fish & Game field officer, Erin Garrick.
Fish & Game funded her research, at Otago University, as part of a nationwide study prompted by a string of poor mallard breeding seasons and concern that populations are being affected by dairy conversions.
The good news from Garrick's research is that there is no significant difference in duckling survival rates between dairy and other pastoral farms.
However, brood-rearing female ducks are found to prefer "unmanaged habitat" such as hedgerows, shelterbelts and rank grass, for nesting sites.
Garrick says this was not unexpected but – alarmingly -- in such habitat ducklings have a lower survival rate.
"In our landscape these habitats are typically thin and linear in [shape], creating ideal travel corridors for predators. While broods may feel safe and protected tucked up in a hedgerow, predators that rely on their [sense of smell] to track prey can easily run along the downwind side of these strips and pick up the scent of, literally, a sitting duck."
Garrick also found that duckling survival is higher when broods are located further from built environment such as buildings and roads.
And, while everyone knows that ducks like water, her figures on the benefit of "ephemeral water" -- temporary ponding from rain in the first 10 days of a duckling's life -- confirm a "huge impact" on survival rates.
Without ephemeral water, cumulative duckling survival to 30 days of age was only 11% for broods raised by yearling females, and 26% for broods raised by adult females. With ephemeral water, duckling survival markedly increased to 28% for broods raised by yearling females, and 46% for broods raised by adult females.
Garrick says ducklings require a high-protein food source, as is readily available in ephemeral water in the form of earthworms forced to the surface.
"This may be why Southland is recognised as a duck factory and as duck enthusiasts we shouldn't be complaining about the weather."
Many Southland farmers are keen duck hunters, she says.
"While not farming ducks directly, they all put ponds on their properties; they want to see lots of ducks around because that will give them a good season opening day."
Garrick suggests three ways farmers can encourage ponding: 1) by not installing sub-surface drainage under pastures; 2) by establishing more seasonal wetlands, as far as possible from the human environment; and 3) by undercutting predators' hunting efficiency by increasing the patch size of unmanaged nesting cover beyond the now common narrow strips.
Wetlands also improve general biodiversity and aesthetic values.
Fish & Game hopes to follow up with further research into predation, she says.
"We found 15-20% of our females were killed while nesting, mostly by feral cats and some by mustelids. So we're curious to find out how abundant those predators are in our landscape.
"We'll also study predators' diets, looking at what proportion is made up of mallards during the nesting and brood rearing period."
