Ibrahim H. Mamkhair
General Commission for Scientific Agricultural Research-
Administration of Plant Protection Research
Damascus University, Faculty of Agriculture
This research work is devoted to study the biology, ecology and control of the Libyan jird, Meriones libycus, which is recognized as one of the most important natural reservoir hosts of the zoonotic continues lishmineasis in Syria and other countries. This jird is also considered as agricultural pest in some regions of the world. The fieldwork was conducted in arid and semiarid areas in the provinces of Rural Damascus and Homs during December 2004 – May 2006. Field trails to evaluate the efficacy of chemical control using locally available rodenticides were conducted. The results for this study were as follow:
The results showed that the Libyan Jird has a long reproduction period, extended from early March to October, while there was no reproduction during winter season. The litter size ranges between 5-6 newborn/litter (5.25 on average). The newborns are naked, with closed eyes, weighing 3.7 g as average. The eyes became open when the newborns were 17 days old. They leave their mothers when 24-25 days old. The females become adult when they are 110 days old, while the males became adult when they are 116-120 days old, where the average of weight at this age is about 108 g.
Sub-adult jirds were trapped mainly during the period May to October, with highest percentage of sub-adults (60%) was recorded in September. On the other hand, no sub-adults were trapped during the period December 2004 to April 2005 and during November and December 2005. The ratio of juveniles and sub-adults is changeable during the reproduction season, where juveniles start to appear in the filed two months after the beginning of the reproduction season.
The sexual ratio was 1:1 between November 2004 to March 2005 and between July to October 2005, while females were dominant on February, May and December 2005.
The Libyan Jird is widely distributed in all study areas, where large colonies of this jird were observed in the aired and semiarid lands in the Syrian Badia. It is the predominant rodent species, while other rodent species were coexisted with the Libyan Jird; Tristrams jird; Meriones tristrami, Wagners Gerbil; Gerbillus dasyurus, the House mouse; Mus musculus and the Social vole; Microtus socialis.
The Libyan Jird mainly constructs complicated burrow systems with long tunnels, about 45 cm under the soil surface; with several openings. The density of burrows entrances ranges 3-9 entrances /burrowing system of the colony’s area. The number of roosting chambers ranges from 0-2, while the number of food chamber reached 0-3.
The tunnels were 433± 237 cm in length and 8.1± 0.8 cm in diameter, while the average volume of burrow system was 2.3×10-2±1.4×10-2 m³.
The dominant plant species was Anabasis syriaca, constituting the main food of Libyan Jird. There are other plant species like Tamarix sp, Artemisia herba alba, Alhagi maurorum, Salsola vermiculata, Solanum nigrum, Atriplex leucoclada and Achilla conferta. The study confirmed that the Libyan Jird foods on the other plant species as Artemisia herba alba and Solanum nigrum.
Field trails were conducted in February 2005 to evaluate the field performance of three rodenticides in controlling colonies of the Libyan Jird Meriones libycus at semi arid lands east to Damascus and Homs provinces. Two percent of Zinc Phosphide wheat baits, 0.005% Brodifacoum ready to use baits, and Aluminum Phosphide (Fumigant) were tested. The active burrows were treated by inserting ten grams of the poisoned baits or by one tablet (3 g) of Aluminume Phosphide. The efficacy of treatments was calculated depending on the number of active burrows pre/post-treatment. Obvious reduction in burrowing activity was registered in Zinc Phosphide, Brodifacoum, Aluminume Phosphide treatments; 95.9%, 91.9%, 81.9% respectively, in comparison to 18.5% in the untreated control. The difference between Zinc Phosphide and Aluminume Phosphide efficacy was not significant, while it was significant between these two rodenticides and Brodifacoum. Symptoms of direct poisoning were observed on mammalian predators in the study area after 24 hours of Zinc Phosphide treatment, indicating serious damage to the nun target species of rodents’ natural enemies in spite of the high potency of this acute rodenticide. The results suggest that inserting one gram only of Zinc Phosphide baits in each active burrow seems to be adequate to achieve high rate of efficacy against the Libyan jird in comparison to the efficacy achieved when 10 grams were inserted.
Another preliminary field experiment was conducted in 2005 to evaluate the efficacy of three quantities (1, 3, and 5 g) of 2% Zinc Phosphide baits against the Libyan Jird. The results showed that the efficacy was 94.3%, 98.1% and 98.3% for the three quantities; 1, 3 and 5 g respectively, while no significant differences were observed. This result suggest that a sufficient control could be achieved by inserting one gram only of Zinc phosphide baits in each active burrow. In this account we may reduce the amount of poisoned baits of Zinc phosphide recommended by the Ministry of Agriculture and Agrarian Reform to control wild rodents to 15%.
The results of volume of burrow system calculation (2.3×10-2±1.4×10-2 m³), suggest that small tablets (0.6 g) of Aluminum phosphide may be sufficient to ensure effective control, and no need to use large tablets (3 g) of this pesticide, when soil humidity is suitable.