Nature groups and experts are calling for more information on how soil investigation works at the Central Catchment Nature Reserve affected native animals.
Without more data, it is impossible to tell if or how the animals were impacted, they said in response to the Land Transport Authority (LTA) statement that findings on its measures to reduce the environmental impact of soil works "were encouraging and validated the mitigation measures developed".
The tests, which involved boring holes up to 70m underground to extract soil samples, were done to explore if the train tunnel for the Cross Island Line can be built under Singapore's largest nature reserve.
The LTA had put in place camera traps and done ground surveys to monitor wildlife for the first part of the tests. There is another ongoing environmental study.
The authorities are considering two alignments for the MRT line - a 4km route, half of which would be under the nature reserve near MacRitchie Reservoir, and a skirting alignment that would take a 9km route around it.
Earlier this month, LTA said that camera traps picked up the presence of animals. Its statement also included two camera-trap photographs of pangolins.
Camera traps used to monitor fauna, like this Sunda pangolin mother and juvenile spotted near Sime Trail by a camera trap last October.
Elaborating yesterday, an LTA spokesman said about 90 camera traps were deployed about three to six months before the soil works started in February last year.
When they ended late last year, monitoring was done for about four to six months.
LTA's findings "suggested that similar animals were present in the areas before and after the works, with various animal groups such as mammals, reptiles and birds captured by the camera traps", she added, without elaborating on the numbers of such animals spotted.
The spokesman said LTA will continue to work with stakeholders "to further analyse the data collected to deepen our understanding of the soil works on fauna activities".
To reduce the impact of the works, LTA had put in place measures, including reducing the number of boreholes and requiring the use of enclosures to reduce engine noise, among others.
The measures were welcomed by nature groups, but they said more data and analysis were needed.
Ms Chloe Tan, spokesman for the Love Our MacRitchie Forest volunteer group, said that the presence of one Sunda pangolin does not prove anything, if there had been more of them in the area in the first place.
Biology lecturer N. Sivasothi noted that the soil investigation works were a serious intrusion into the protected nature reserve, and it was important to substantiate statements about their impact.
"Right now, other than the two photographs of the pangolins, there is no scientific data to verify if the mitigation measures really worked," he said.